If there were any intelligent life underwater it would most likely be some kind of octopus or other cephalopod. Octopus are very intelligent and are
good problem solvers which makes them very near impossible to keep as pets because they are always escaping.
As for technology, if they have any is probably very limited, but probably resembles nothing like ours because they would have found other
resources.
As for food, fish would be a main source of diet, and plants can grow at great depths in virtually no sunlight due to heat from volcanic vents which
is sufficient to support a small colony living animals.
I would think that any intelligent species is probably unaware of us, just as we are unaware of them. Think of the pressures, just as you can not go
to great pressures from low pressure, you also cannot go from great pressure to low pressure. So anything on the bottom of the ocean is likely stuck
there.



now i would pay good money to see that 
CATFISH 