You're saying you wouldn't be afraid when a Dopefish would pop up behind you???
Dopefish eat you whole, as opposed to sharks which usually need at least a few chomps.
I think a Dopefish would actually swallow the whole oxygen container before anybody had a chance of aiming at it, so it wouldn't be so easily taken out either.
Also Dopefish burp, and... uhm, I'm sure some people are afraid of burping.