Not sure about the Bahamas but here in Jamaica a good depth finder is a MUST. Not only do we target different species at different depths, but if fish are biting in a certain depth, we use that same depth when we change spots.
Granted our fish may not be as plentiful as the Bahamas but I would be lost without my depth recorder for trolling as well as deep dropping. We are not fishing an edge but fish offshore banks that are pretty much vertical.
On my boat I have a Furuno 582L. It may not show the fish as more powerful machines will but I read depths up to 3000ft.
I would not fish without it.