Don’t believe that sea angels are real? Just search ‘sea angel’ on the internet and you will become a believer … but before we explore what they are, have a close look and marvel at their beauty and how well they fit their common name.

‘Sea angels’ are small free-swimming sea slugs and can be up to 5cm long apparently. They swim head-up in the water like a hovering angel, using tiny wing-like fins that are suggested to be an evolutionary adaptation of their sea slug foot. There are more obvious slug-like sea slugs but even some of them are able to swim up into the water using more of a frilled skirt-like foot - the most exotic being the ‘Spanish dancer’ sea slug, that at up to 60cm, swim (or dance?) like a spirited red Santa cape but they live in warmer waters.

Sea angels are found right around the global ocean. They are not particularly strong swimmers and drift with the ocean currents making them part of the plankton; being animals they are part of the zooplankton. Remember, plankton does not need to be tiny, dustbin sized British barrel jellyfish are plankton too. ‘Plankton’ simply means drifter - to be carried by the tides and currents.

I first came across sea angels, myself, just before the Christmas of 1981 when I was a student in Fife (Scotland) – I’d finished my end of term exams and had the mad idea to go for a shallow water scuba dive just out from our student accommodation. The east coast waters of Scotland are not that warm at any time of year, so anything but in December and I only had a wet suit then. I remember that there was even frost on the ground but I was young and keen. I did take an added precaution of putting my suit on in a warm shower so that the cold seawater of the dive wouldn’t flush through as quickly. I did everything slowly and gently to keep the warmer water in my suit and semi-drifted around the shallow rock reefs and in amongst their forests of kelp seaweed. The weather was very calm and the water was beautifully clear, as it can be in winter. I loved watching the crabs, anemones and sea snails all going about their everyday fight for life and totally oblivious of the big clumsy zoo-plankton (me!) watching them.

I came across two sea angels on that dive - just hovering, almost in slow-motion, in midwater before me. Even though I was in Scotland to study marine biology, at that time I’d never seen or heard of anything quite like sea angels before. I probably had a bit of the excitement and expectation of Christmas in my head and I couldn’t believe what I was seeing - tiny 2-3cm long angels ‘flying’ in the water in front of me! I spent some time just floating in the water with them, mesmerised by their beauty in time, motion and form. I didn’t have an underwater camera then so had to etch their picture into my memory to identify them later. I don’t remember if the cold got to me first or my air ran low but I eventually had to leave them and headed back to rinse myself and my kit off in a warm shower.

My student flat was only 100m from the famous Gatty Marine Laboratory, so I knew exactly where and who to ask. We decided that they were most probably the free-swimming mollusc Clione limacine … despite the obvious connection, I’m not sure that ‘sea angel’ was a name given to them back then? A lot of marine species have been given descriptive common names to help memorise them.

Our marine (& estuarine) life never fails to amaze me and fill me with wonder and awe – so so often, after a good rockpooling tide, dive or snorkel, I discover something I’ve not seen before and have to look up … it’s what convinces me that we really need to respect and care for our ocean … that upon which we so much depend ourselves.

Here are a few gems about the sea angels that I have researched and learnt since;

· Sea angels are actually quite voracious predators, hunting and feeding on a relatively close relative of theirs, the sea butterfly - a free-swimming sea snail. I’ve only seen sea angels maybe a couple of times since but I’ve yet to see a sea butterfly.

· When sea angels hunt down their prey, they incredibly push out a crown of horn-like tentacles - changing their demeanour from angel to demon in the blink of an eye!

· I’ve never tried to eat one but apparently some sea angels pack a bit of a chemical punch for any fish trying to eat them … they certainly wouldn’t be hard for a fish to spot!

On behalf of all Nature Noters, may we wish everyone a very healthy, sustainable and happy Christmas and a blue-green New Year!

PS The Christmas picture that accompanies these notes is obviously very much photo-shopped, as baubles underwater would clearly float up!