Don't know much about fish, TTT, despite being a Pisces:-) However, watching QI last night i learned that one of the slowest fish, the sea-horse, is also the most predatory successful creature underwater with a 'kill rate' of over 90%. The shape of their heads allows them to (very slowly) approach their prey before hoovering them up with their snouts. Doesn't sound that impressive until you realise that most of their prey can swim much, much faster than the underwater dobbin:-)