The joy of Sea Slugs!

, 01 August 2022
The joy of Sea Slugs!
Coryphella Lineata © Paul Naylor

By Olle Akesson

Marine Officer

I spend a lot of time telling people that the seas around the UK aren’t the murky green waters that they appear to be. That they may not look as exciting as a tropical coral reef, but delve a little deeper and they quickly reveal a huge amount of beautiful and colourful life.

One Saturday, we dived the wreck a steam trawler, just south of Brighton and as we descended through the water column I must admit I thought it was going to be a dull dive. At the moment the seas are getting warmer causing the plankton to go into overdrive and the visibility underwater has dropped significantly; at 15 metres depth everything had gone dark green and at 20 metres there was very little natural light. We used torches but could still only see about a metre but as we slowly swam around the wreck our limited view meant focusing on small areas which revealed many of the little things living under the sea which are often overlooked. Amongst these are Sea Slugs, or nudibranchs. These are amazing little creatures, less than a couple of centimetres long. Nudibranch translates to ‘naked lung’ as their gills are on the outside of the body in finger-like projections and they are incredibly colourful. Depending on the species they can be bright yellow, purple, deep red or a beautiful, almost transparent blue. I love seeing these little creatures and on Saturday I saw more nudibranchs than I've ever seen before. During a 45 min dive we swam about 40 metres and easily saw over 40 individual animals from seven different species: Violet Sea Slug (Flabellina pedata), Coryphella lineata, Scarlet Lady (Coryphella browni), Crystal Sea Slug (Janolus cristatus), Yellow-edged Polycera (Polycera faeroensis), Sea Hare (Aplysia punctate) and Common Grey Sea Slug (Aeolidia papillosa).

What I thought was going to be a miserable dive turned out to be one of the best ones of this year.

Yellow-edged Polycera (Polycera faeroensis) © Paul Naylor

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  • richard fulton:

    we see them off the beach in selsey when we dive there,
    its a very good dive so much to see,lots of creatures go there to breed.its not deep and no need for boats.
    its the best sussex dive i think

    25 May 2016 20:06:22