Nudibranchs

To the casual observer, nudibranchs are tiny, colourful slugs crawling over coral. To the diver who stops to look closely, they are among the most astonishing creatures in the ocean — dozens of species, each more vividly patterned than the last, their colours serving as warnings to would-be predators or as camouflage against specific prey items.

Thailand’s Species

Thailand hosts hundreds of nudibranch species across its two sea regions. The variety is staggering: from the spectacular Spanish dancer (Hexabranchus sanguineus) — a 30cm crimson species that swims by undulating its body — to microscopic aeolid nudibranchs only a few millimetres long, their cerata (finger-like projections) incorporating the stinging cells of the anemones they feed on.

Where to Find Them

Richelieu Rock in the Surin Islands may be Thailand’s premier nudibranch site — the extraordinary density of life on every surface means nudibranchs are everywhere, and their variety is exceptional. The Similan Islands are similarly productive. In the Gulf, Koh Tao has good nudibranch diversity on its reef sites, particularly for macro photography practitioners.

Photographing Nudibranchs

Nudibranchs are the primary focus of many serious underwater macro photographers. A 60mm or 100mm macro lens, excellent buoyancy control, and patience are the prerequisites. The reward is images of extraordinary beauty — alien creatures of impossible colour on a canvas of coral.