Molluscs & Crustaceans

As the second-largest phylum in the animal kingdom, Mollusca offers a dazzling spectrum of marine life. Finding them is a mixed bag—some are nearly impossible to miss, while others require incredible patience and a sharp eye to spot against the backdrop of a busy reef.

Here is a look at the three major classes you are most likely to encounter:

Queen conch - Florida Keys USA

Flamingo tongue snail - San Salvador Bahamas

Sap-sucking slug - San Salvador Bahamas

Molluscs

Gastropods (Snails, Sea Slugs, and Nudibranchs):

Heavy-shelled sea snails, like conchs, are often the easiest to spot as they slowly bulldoze across the sandy bottom. On the opposite end of the spectrum are the sea slugs and nudibranchs. These shell-less wonders are frequently tiny and perfectly camouflaged against the sponges and hydroids they feed on. However, if you have the patience to seek them out—and perhaps a good macro video light to illuminate them—they are an endlessly fascinating group, boasting some of the most surreal shapes and striking neon colors in the ocean.

Bivalves (Clams, Oysters, and Scallops):

This group is generally much easier to recognize, not least because many of their cousins regularly end up on our dinner plates. Underwater, you will typically spot them firmly embedded in the hard reef structure or resting directly on the sediment, filter-feeding with their two hinged shells slightly ajar.

Caribbean reef squid - Roatan Honduras

Octopus - Andaman Islands (Credit: Ummeed Mistry / Ocean Image Bank)

Cephalopods (Octopuses, Squid, and Cuttlefish):

Encountering a cephalopod is always a thrilling, albeit rare, surprise. Because they possess remarkable intelligence and shape-shifting camouflage, they can easily blend right into the substrate. Many species are highly reclusive, preferring to stay tightly wedged inside rocky crevices during the day, only venturing out to hunt under the cover of darkness.

More pictures will be added overtime as I am able to spot some of those animals and capture them on camera.

Cuttlefish (Credit: David P. Robinson / Ocean Image Bank)

Maxima Clams - Red Sea (Credit: Jake Adams)

European flat oyster (Credit: Stephane Pouvreau Ifremer)

Great scallop (Credit: Paul Naylor)

Crustaceans—encompassing a highly diverse group of species like crabs, lobsters, and shrimp—are defined by their hard, jointed exoskeletons that act as a protective suit of armor. Because they are generally reclusive and spend their days tucked deeply inside rocky crevices or coral heads, they are notoriously difficult to find while the sun is up. However, night dives offer a fantastic opportunity to finally spot them in the open, as they confidently emerge from the reef to hunt and forage under the cover of darkness.