I am looking for a underwater drill, any info proir to buying would be helpful.

using the old hand style turn crank is what I still use today. you can get them on e bay. other than that pneumatic drills can be usually picked up relatively cheap. Hydraulics are big bucks what are you looking for?

we use a small hand drill and cheap pneumatic drills

I just use a cheap air drill, works fine and oil up with veg oil afterwards

A cheap pneumatic drill works fine for me, just make sure to keep it oiled good.