Has anyone had experiences with aggressive sea animals?
That question is far broader than sharks, and if you substitute dangerous for aggressive, it's even broader. I dive Florida and the Caribbean, not the U.K. You will probably travel to some tropical destinations at times. In terms of hazardous wildlife, my concerns and approach is:
1.) Large barracuda - probably not bad news in good viz. water if I don't blunder into its close personal space, such as messing around a wreck. Take pictures, don't get within several feet.
2.) Sharks - most are not deemed significantly dangerous to humans, including all I've been in the water with so far. Watch, but don't freak out. I've yet to deal with encountering a great white or tiger shark. I suspect it would be unwise to abruptly flee, as a prey might, perhaps triggered a predator response. Try to master your fear, gradually move toward cover/structure/bottom if you reasonably can, and watch it closely I would think. I think the idea of purging if it approaches is probably worthwhile.
3.) Big moray eels - Watch the eel for hostile response, and absent that, I'll get to maybe a yard from one. But some people feed them lion fish, so be mindful it might approach looking for one. From what I understand, even if a big green moray gets in contact, it doesn't necessarily follow that it's going to bite you.
4.) Scorpionfish - similar to stone fish, highly camouflaged fish with venomous spines, avoided by staying off the bottom. But if you wreck dive in current and need to grasp part of the structure to hold on, be mindful this sort of thing can be there. One was about a yard from my hand holding onto an algae-covered wreck in October, and it was hard to see! One forum member touching bottom momentarily with a finger got nailed by a very small stone fish and had incredible pain and serious medical complications.
5.) Lionfish - I don't normally 'worry' about them, but read an account of someone on a night dive getting nailed in the leg by one minding his own business. Evidently on occasion they can be aggressive.
6.) Jellyfish & Portugese Man-O-War. Some such organisms can have tentacles dangling well below the bell, and blundering into them could be bad news.
7.) Stingrays (in some areas, torpedo rays) - usually not likely to be trouble if you stay off the bottom. In the Florida Keys out of Key Largo, it's fairly shallow reef diving, often over some sand, and some fairly big ones cover themselves and are hard to see. Swimming right over one might not be the best idea. I understand it's also possible to step on stingrays in the shallows.
8.) I have never dove where titan triggerfish occur, but if you do, you need to know about them.
9.) I have dove close enough to a big rainbow parrotfish to worry I was agitating it. I don't know whether they've ever freaked and bitten anybody, but those jaws could do some damage if so.
10.) Fireworms (a.k.a. bristleworms) are something I didn't worry about as long as I stayed off the bottom, until somebody here mentioned in a penetration your bubbles could dislodge one overhead. Probably a paranoid fear since I don't do penetration dives, but I have done swim throughs. Which could potentially put me in close quarters with a lion fish or moray, too.
So, when I think about hazardous wildlife (and I left off fire coral, a hazard on mooring lines and when shore diving where there's surge to shove you into it), sharks are just one thing I think about. But none of these things is likely to injure me as long as I don't blunder right into or try to grab or hand feed it.
Richard.
