deep diving to get rich must be something new, i haven't heard of it.
kelp prices on my server sucks, hopefully it's better for others.
the main things i do know that people spend time in the water for is that fishing pole in desolace and some of the pearls, but even that isn't a great money-maker for the time involved.
like others said, without being an engineer (deep dive helmet), warlock/druid, or alchemist, you can do the other tradeskills with any class.