the marine life

The rich waters of Costa Rica offer an unbelievable underwater world, with such a diversity and abundance of marine life. With fish everywhere, as well as mammals, reptiles, molluscs, sponges, urchins and soft corals, these waters truly are phenomenal . The dive locations at the Catalinas are a sight to behold.  Here is a run down of just some of the marine life out on the Catalinas, Costa Rica.

10 of the best

manta ray (manta birostris)

The largest type of ray in the world, the giant oceanic Manta ray can grow to a disc size of up to 7m (23ft) with a weight of about 1350kg (2980lbs) but generally they are around 4.5m (15ft).They are filter feeders and consume large quantities of zooplankton in the form of shrimp, krill, and planktonic crabs. At the front, it has a pair of cephalic fins which are forward extensions of the pectoral fins. While feeding, the cephalic fins are spread to channel the prey into its mouth, and the small particles are sifted from the water by the tissue between the gill arches. The Manta ray does not possess a spiny tail. They will sometimes visit a cleaning station, more often around high tide, where cleaner fish go to work. These rays must continuously swim in order to allow for respiration, as they channel water over their gills.

harlequin shrimp (hymenocera picta)

These beautiful little shrimp are found through the central and eastern Pacific. These cream colored arthropods are decorated with deep pinkish-purple spots. The shrimp have two walking legs on each side of the thorax, along with a pair of large claws towards the front. The claws and eyes appear flattened and thin, and on the head the shrimp have petal-looking sensory antennules to smell out their prey. Harlequin shrimps are usually in pairs where they hunt and defend their homes together, generally with the same partner for life.  The female is the larger of the two, reaching up to 5cm (2in) and produces between 100 to 5000 eggs per season. Out on the Catalinas they feed exclusively on the blue seastar (phataria unifascialis). Working as a team they flip the seastar on its back and feed on its tube feet and soft tissues.

whitetip reef shark (triaenodon obesus)

Normally between 1.2m-1.8m (4ft-6ft) in length. The Whitetip reef shark has a slim body and a short, broad head. The snout is flattened and blunt, with tubular skin flaps beside the nostrils, oval eyes with vertical pupils, and white-tipped dorsal and caudal fins. Unlike many shark species, which must constantly swim to breathe, the Whitetip reef shark can pump water over its gills and so is able to lie still. They prefer very clear water and are normally found at depths of 8m–40m (26ft–131ft). At the Catalinas these sharks are generally found lying on sandy patches or channels. Whitetip reef sharks are not territorial and share their home ranges with others of their species. Predominately feeding at night they dine mainly on bony fish, as well as eels, octopus, lobsters, and crabs.

hawksbill turtle (eretmochelys imbricata bissa)

An adult Hawksbill can have a shell around 1m (3.3ft) in length, and these marine reptiles can weigh around 70kg (155lbs). Their strikingly colored carapace, or shell, comprises of an amber background decorated with light and dark streaks combining to form an irregular overlaying pattern, with predominantly black and mottled-brown colors radiating to the sides. The Hawksbill has a distinctive way in which the scutes, or plates of the shell, overlap. This overlapping results in them having a serrated appearance to the rear margins of the carapace. The Hawksbill possess a beak-like mouth which is more sharply pronounced and hooked when compared with other turtle species. Hawksbills feed mainly on sponges, however these turtles are omnivorous and will also eat molluscs, marine algae, crustaceans, sea urchins, fish, and jellyfish.

white spotted boxfish (ostracion meleagris)

This is a species of boxfish found in the eastern Pacific Ocean. It is found on rock reefs of the Catalinas at a depth from 5m-20m (16ft-65ft). This species can grow up to a length of 25cm (9.8in), although when fortunate enough to see one, they are normally in the range of 10cm-15cm (4in-6in). Males and females differ in colour. Females and juveniles are dark brown or near black, with white spots. The males are much more elaborate in both colour and pattern. The males have a blue body with white dots and bright orange/yellow mottling effect on its back and edges. Males swim around more openly than females. Females will often be in the close vicinity of the males. They feed on sponges, molluscs, copepods, and algae.

common octopus (octopus vulgaris)

More active at night when they generally feed, this amazing cephalopod will spend the day time mainly hiding in rocks and cracks in the basalt formations. On the Catalinas they are found anywhere between 8m-30m (25ft-100ft). They have a whole host of amazing adaptations. The Common octopus uses gills as its respiratory surface and they have three hearts. Most impressive is their ability to almost instantaneously match the colours, patterns, and even textures of its surroundings by using a network of pigment cells and specialized muscles in its skin. Their soft bodies can squeeze into impossibly small cracks and crevices.  They can grow to about 1.3m (4ft) in length. Their main pray are crayfish, crabs and bivalve molluscs.

nudibranch (nudibranchia)

These are a group of soft-bodied, marine gastropod molluscs. Currently, about 2,300 valid species of Nudibranchs are known and have been catagorised. They are noted for their often extraordinary colours and striking forms.  Their forms and colouration vary greatly, as do their size. Of the Nudibranch found on the Catalinas, they range in size from 0.5cm-10cm (0.2in-4in) and can be found throughout the water column from 5m-25m (16ft-80ft). Nudibranchs are carnivorous and are known to feed on sponges, others on hydroids, others on bryozoans, and others with sea squirts (tunicate). Nudibranchs are hermaphroditic and have a set of reproductive organs for both sexes but they cannot fertilize themselves.

spotted eagle ray (aetobatus narinari)

This species of ray has a flattened body and the head has a rounded snout. The colouration on its back is black or deep blue covered with numerous white spots, and its ventral surface is white. The pectoral fins are extremely pronounced, resulting in the ray possessing wing-like appendages used for primary propulsion. The Spotted eagle ray has a heavily modified caudal fin resembling a whip-like tail.  Their tails are longer than those of other rays and may have 2–6 venomous spines just behind the pelvic fins. They can be around 1m-3m (3ft-10ft) in width. Without the tail they can measure 1.2m-2m (3.5ft-6.6ft), with tail up to 6m (20ft).  Spotted eagle rays have heavy dental plates which they use to crush their hard-shelled prey, and will feed on bivalve shellfish, shrimp, crabs, annelids, octopus, whelks, and small fish.

pacific seahorse (hippocampus ingens)

One of the largest of the 34 known species of seahorses in the world, it can reach up to 30cm (12in). They range in colors based on the location where they live. To help them avoid predators they have the ability to blend in to what is all around them. They are often gold, maroon, brown, white, or a combination of colors. Plankton, small microorganisms, and crustaceans make up the diet for the Pacific seahorse. They swallow their food whole so it has to be small enough to fit into the snout. Seahorses lack teeth, and prey is consumed by sucking it through their bony snout with a rapid snap of the head. Seahorses will feed often, as they don’t have a digestive system. When it comes to reproduction the female will deposit eggs into the male. The male has a brood pouch where the eggs are fertilized and will remain safe until hatched.

Juveniles and adults have markedly different appearances. The difference in appearance between juvenile and adult novaculichthys taeniourus is so striking, the common name Rockmover wrasse is used for adults and Dragon wrasse is used for juveniles. In juveniles, the first two dorsal fin spines are long and extended, drooping over the fish's forehead to form a "cowlick". As the fish matures, the elongated rays are lost. Young juveniles found on the Catalinas are usually green, turning burgundy to brownish. Both are spotted in white. Juveniles favour shallow areas on rubble among large patch reefs. Juveniles resemble algae and mimic the movements of detached, drifting seaweed by swaying back and forth in the currents to avoid predation. 

juvenile rock mover wrasse (novaculichthys taeniourus)

10 every dive sightings

panamic green moray eel (gymnothorax castaneus)

The Panamic green moray eel is a large moray eel in the Pacific Ocean. It is very elongated and muscular, and grows to about 1.5m (5ft) in length. On the Catalinas it is found in and amongst boulders and the reef, at depths between 5m-30m (16ft-100ft). The large mouth has caniniform teeth and the snout is usually sharply pointed. They lack pectoral fins, but the dorsal and anal fin are well developed, though largely hidden by tissue.  Usually feeding at night on fish and a variety of invertebrates such as crabs, shrimps and octopus. Their small circular gills located on the flanks far behind the mouth, require the moray to constantly open and close its mouth. This is an action required for respiration, not a sign of aggression.

king angelfish (holacanthus passer)

Found on every site of the Catalinas. These fish can grow up to 30cm (12in) and are found throughout the water column from the surface down to 30m (100ft). Adults most commonly have a dark slate blue body with yellow pectoral and caudal fins. They have a distinctive and identifying bold white vertical stripe, originating at the rear margin of the pectoral fin and terminating at the upper body margin. These fish are omnivorous and feed on a large variety of animal and plant life, although out here the eggs of the Sergeant Majors seem to be a particular favourite. King angelfish may be seen on their own, in pairs, or sometimes in fairly large schools.

barberfish (johnrandallia nigrirostris)

This fish is in the family of butterflyfish, and is found on all sites throughout the Catalinas. This species has a yellow compressed body and has black bands along the base of its dorsal fin, and on its snout and forehead. It has a small protractile mouth with a black mask around its eyes. Here, they are normally around 10cm-15cm (4in-6in). The barber fish are known to feed on algae, gastropods, and small crustaceans. Out on the Catalinas they are also a main cleaning fish, picking parasites from larger species. As with the King Angelfish, these fish are also keen on the eggs of the Sergeant Major. These fish are generally seen in large groups, and have a tendency to follow divers along on parts of the dive, looking for something to stir.

pacific ladyfish (elops affinis)

Also known as the Machete and the Pacific Tenpounder. They are known to be highly carnivorous, feeding on smaller fish and crustaceans. These can reach almost 1m (3.3ft) in length but are normally around 50cm (20in). Pacific Ladyfish are elongated, slender fish with a compact oval cross section and large deeply forked tail or caudal fin with long, slender symmetrical lobes. The small head is pointed and both the eyes and terminal mouth are quite large. The colour is silvery on the sides and silvery green or blue on the back. The dorsal fin and tail are dusky. The pectoral, pelvic, and anal fins are pale, and may be even yellowish.  This is a schooling fish and around here there are normally found hanging out anywhere between 10m-15m (33ft-50ft).

panamic barnacle blenny (acanthemblemaria hancocki)

Also known as a Hancock's bleeny, this is a species of Chaenopsid blenny found on rocks and reefs around Costa Rica. Normally living in the empty mollusc bore holes on the rocky reefs, they feed on zooplankton. The Panamic barnacle blenny has a predominantly green head with a large dark brown spot behind its eye. It also has red lips, a red iris and red on the front of its dorsal fin. The body of this fish is seldom seen as they will take up residence in a small crevice in the rocks. Sometimes they will quickly dart out of the security of their hole as they race as fast as they can to snatch food from the water column, while trying not to be eaten by the other fish. They can measure up to 4cm (1.5in). Being so tiny, you really need to get up close to see the exquisite beauty of the tiny details which decorate this groovy little fish.

spottail grunts (haemulon maculicauda)

This reef associated species can be found in schools around coastal reefs during the day, dispersing over sandy substrate at night to depths of 33 m. It can also be found at deep rocky walls as well as exposed shallow rocky reefs. This species is endemic to the eastern Pacific. Can be found in such numbers that it is quite literally engulfing. This fish appears silvery grey with lines. Each scale bearing a pearly blue spot, the spots appearing to form lines following the scale series with yellowish fins and a large spot on the caudal peduncle. Normally around 25cm (10in) in length, they have a terminal mouth. They are known to feed on plankton in the open water, but some seek small prey on the seabed.

chancho surgeonfish (prionurus laticlavius)

Also known as the Razor surgeonfish. This fish has an oval body which is compressed. It has a steep head profile, and the eyes are situated high on the head with a small mouth positioned low. Instead of having the usual scalpel mark on the caudal peduncle this surgeonfish has 3 bony nobs along each side of the middle of tail base, similar to thorns on a rose bush. Grey body colour with a bright yellow tail fin. It has a few black spots on the tail base and a dark bar running vertically through the eye, and another through the shoulder.  Small juveniles are mainly bright all over yellow. These fish are normally in large schools and can get to around 30cm-45cm (12in-18in) in size. They are normally found at depths anywhere between 5m-30m.

arrow crab (stenorhynchus debilis)

The Arrow crab is named because of its head and body resembling an arrow. It has eight spider-like legs and has a head that is exceptionally pointed at the tip. Normally 5cm-12cm (2in-5in). Colouration is variable in this species with the body normally golden, yellow or cream, marked with brown, black or iridescent-blue lines. The legs are reddish or yellow. Normally found hiding out under a boulder, or in inhabiting small caves or crevices. This tiny crustacean is found on all of our dive sites of the Catalinas, and can be found throughout the whole water column. The Arrow crab is mainly a nocturnal scavenger, but is also occasionally carnivorous, preying on small feather duster worms (sabellidae) and other tiny reef invertebrates.

spotted sharpnose puffer (canthigaster punctatissima)

This little puffer is found on all sites and is generally down between 5m-15m (18ft-50ft). It is reddish brown with white spots and is normally around 3cm-6cm (1in-2.5in) in length. It lacks pelvic fins, but has learned to use the pectoral fins to move around. It is an opportunistic generalist, feeding on a variety of vertebrate and invertebrate prey. It has also been reported that this species is also known to be a carnivorous cleaner of the green sea turtle (chelonia mydas). As a defensive mechanism, when frightened or disturbed they are capable of inflating their abdomens with water. They can also produce Tetrodotoxin and Saxitoxin in the skin, which are both two potent neurotoxins.

panamic sergeant major (abudefduf troschelii)

Generally of a length around 10cm-15cm (4in-6in), found on all sites and normally at a depth of between 0m-15m (0ft-50ft). The Sergeant Major has a fairly deep body which is oval and compressed. It has a continuous dorsal fin and a forked caudal fin. The ground colouration of the body is white with five bright black vertical stripes on the sides, a black spot on the base of the pectoral fin and a bright yellow back. They will feed on plankton at the surface or mid-water, as well as graze on benthic invertebrates and algae on the reef. They form distinct pairings during breeding, and during reproduction the eggs are demersal and adhere to the rock reef. It is the male’s responsibility to both guard and aerate the eggs.

one love

experience the blue with

100% passionate. 100% professional

ocean divers

one love

follow us on facebook
  • Facebook Social Icon
  • youtubelogo
  • TripAdvisorlogo
see tripadvisor reviews
watch us on youtube
office hours : 7am - 4pm daily
   :   +506 8466 1580
call/text or