depth finders that read that deep are lovely to have but far from necessary, GPS to re-locate a hot drop is far more valuable to me.
use charts to locate likely areas or better ask locally for GPS numbers, Bahamians can be cagey about giving out the real honey holes though.
I use a carpet bombing technique where I will make a string of drops from shallow to deep, if nothing after 5 mins on the bottom, move a ways down the drop off and try again.
read my article in the latest SFSF mag