What does 'nudibranch' mean? The name comes from Latin 'nudus' meaning 'naked' and the Greek 'brankia' meaning gills, so nudibranch literally means 'naked gills'. This is thought to refer to their visible feathery gills, and their lack of shell.

Why are nudibranchs so colourful? Nudibranchs are often brightly coloured as a form of defence, to warn predators that they are toxic, or to use as camouflage to blend into the colourful reefs.

How long do nudibranchs live? A nudibranch's lifespan is usually up to one year, but the oldest one on record was four years old.

What do nudibranchs eat? All true nudibranchs are carnivores, meaning that they eat other animals. Due to the huge number of species of nudibranchs, there are lots of different things that they eat. These include (deep breath) sponges, hydroids, jellyfish, anemones, soft corals, bryozoan, crustaceans, fish and, sometimes, other nudibranchs. However, some species of nudibranchs don't need to eat; as larvae, they will consume algae, which will power them through the rest of their lives through the process of photosynthesis.

How do nudibranchs eat? They have something known as a radula, which is like a combination of tiny teeth and a tongue, that allows them to munch on corals, sponges and other food.

What eats nudibranchs? Many marine animals enjoy munching on nudibranchs, including turtles, crabs, starfish and several fish species, specifically wrasses and butterfly fish.

Do nudibranchs always live on the seafloor? No. Some nudibranchs are pelagic (meaning that they live in the open ocean).

Are nudibranchs dangerous to humans? Yes. Some species of nudibranchs, such as the blue dragon, have toxic properties. This comes from their food source, the Portuguese man o' war, so as with all marine life, look but don't touch.

Can a nudibranch sting? Yes, some, such as aeolid nudibranchs, can sting because they have stolen stinging properties from their prey, typically jellyfish.

How do nudibranchs communicate? Nudibranchs leave a trail of slime, which is a unique marker filled with chemicals to communicate to find a mate or to warn of predators nearby.

What is the biggest nudibranch? The biggest nudibranch is the Spanish dancer, which has been known to reach up to 60cm.

What is the smallest nudibranch? Lots of nudibranchs are small, but one of the smallest is the three lined nudi, Flabellina trilineata, which is often only around six millimetres.

How fast are nudibranchs? Nudis are slow-moving creatures, but some have been recorded to slide at speeds of five millimetres per second. But mostly they move around 0.03mph.

How many eggs can a nudibranch lay in a lifetime? Depending on the species, a single nudibranch can lay millions of eggs in a lifetime.

​When is the best time to see nudibranch? As nudibranchs can be seen all over the world in so many different habitats, they can be seen at any time of year (just be sure to check the best time to dive in the specific destination you are heading to). Likewise, some species come out at night, while others are more likely to be seen during the day, so the best time of day will depend on the specific species you are keen to spot.

How do you pronounce nudibranchs? Nudibranch is most commonly pronounced like 'noo-dih-brank', but some pronounce it as 'noo-dih-bronk'. If in doubt, use the shortening of 'nudis' (pronounced 'noo-dees').

What are the most famous nudibranchs? Some of the species we mentioned above are among the most well-known nudis, such as the Spanish Dancer, 'Shaun the Sheep' and 'Pikachu' nudibranchs.

What are the best nudibranch to photograph? Some of our favourites include the Spanish Dancer, as they are larger than most nudibranchs and look beautiful when swimming; neon slugs (Nembrotha kubaryana), as their neon greens and oranges are vibrant against their back bodies, so they make striking subjects; and 'Shaun the Sheep' or Sacoglossa nudibranchs, as they have particularly cute faces and they are also photosynthetic (meaning they store chloroplasts from algae to produce energy), giving them a wonderfully vibrant green colour.