My initial* thoughts:
Dolphins*- Beautiful, intelligent creatures who live in pods, love each other and look after each other, they have advanced communication skills, are able to use reason and solve things, they like to have fun, smile and be happy, they like to be exhibitionists and impress each other and humans, incredible dexterity and acrobatics. They have saved many humans from shark attacks. Capitivity kills their spirit and they have been known to give up, it is hugely cruel.
(* Re: Dolphins - Second thoughts since reading this thread - Please tell me this isn’t true, dolphins are bastard rapists? They kill countless babies and other harmless creatures? Nooooooooo. I can’t believe it. You are basically telling me they are one fin away from being the Ted Bundy’s of the sea. This can’t be happening. I don’t remember David Attenborough saying a single word on this subject).
Orca - Large and powerful, creepy looking creatures but also beautiful at the same time, live in groups, could kill you as soon as look at you if they wanted to. They are intelligent and can use reason and solve things. I’ve seen them (on TV) group together and follow a mother and baby whale (not sure which type) for miles trying to separate them. Then drown the baby and eat just the lower jaw I think it was because it’s a delicacy. To me that’s sinister and downright nasty. Yes I know they are wild creatures but seriously? They also hate being in captivity, it is so cruel and they have been known to plot and kill their handlers by drowning them.
Whale - Large and powerful. Some of them survive on eating plankton, tons of the stuff. Quite incredible creatures.
Sharks - They get a bad press due to Jaws mainly. Great whites and tiger sharks and the like are amazingly effective predators, they will attack, kill and eat each other and most other things that take their fancy. So impressive and they have hardly evolved because they are virtually perfect in design. There are so many other types of sharks that are no threat to humans but they all seem to be lumped together as nasty buggers. Sharks are under threat from humans big time.
Sawfish - Don’t know much about them but they are bound to play an important part in the chain like all other sea creatures.
Sea Horses - Yes, I love them! Always have. So beautiful, majestic and cute. They seem quite calm and laid back. The Dad’s incubate the babies I understand - Brilliant! Make me feel warm and fuzzy.
I was given a dried sea horse when I was little, it was a prized possession of mine, I felt so lucky to have it. That’s until I was a bit older and realised the poor creature had died just so someone could make some money out of it and I could look at it from time to time. I buried it in the garden after that and felt so sad and guilty about it.
Crab - Sharp pincers, excellent armour, good little hunters, often scampering about looking busy. I don’t mind them.
Sea Otter - Ingenious and clever, are intelligent and can solve things. Always thought they looked cute, furry and had their shit together.
Octopus - A bit creepy, imagine they are slimy, intelligent and can solve puzzles, loads of different types, don’t really warm to them.
Eel - Ick! Sorry I don’t like them. They seem slimy, wriggling and writhing around, can’t be doing with them. But it’s not their fault.
Starfish - Nice looking, what’s not to like really, seem quite harmless as far as I know. They have their own niche in the sea world. Yeah I like them.
Ray - Beautiful creatures, but frightening because most seem to be capable of killing you if they feel like it. Manta rays seem to be particularly interesting and majestic when I’ve seen them in big groups on the tv.
I like the fact there is so much mystery surrounding the sea and it’s sea life. So much left to discover. It’s a magical place but also eery at times.
I worry about what is happening to our seas and oceans. Most governments are not doing anywhere near enough to protect them. Humans have caused so much damage it’s awful.
Interesting thread OP, good luck with your creative writing. I expect you’ll have plenty to ponder over on this thread!