They're not spiders, their pycnogonids. They are chelicerates, like arachnids and xiphosurans (horseshore crabs) and eurypterids (sea scorpions), but apart from that, totally different and TOTALLY benthic, so you won't find them floating anywhere. You might find a tiny one in the mud at the bottom, if you are
really lucky, and the pycnogonid is really lost.
But seriously, you wouldn't react to them n the same way as a spider. They may have superficially similar legs, but trust me, in the flesh they give off a completely different vibe, you couldn't classify a fear of them as arachnophobia, it would be "pycnogonophobia".
Teeth are not an indication of aggression. I mean, a shark wouldn't attack you, why should they? Most are really small anyway, their teeth look huge in the pictures, but they're tiny. Also, no poison. Hell, a spray underwater? WTF?
If you met a harmless viper fish, you'll have bigger problems than your encounter to deal with. Like the lack of air and searing pressure kilometers down.