How to make $7500 a minute.

[Captain Revenge]

Potentially make it in a minute, your boating skills or lack there of will matter, so will keeping an eye on your boat, this will work with or without scuba gear. Just east of the ship the SS Bulker are 2 bridges that look the same, 1 roadway 'Signal street' and 1 railroad, between the 2 is a sunken barge with a gold briefcase with $7500 in it, pull up in boat or wave runner go get briefcase, come back up get in boat ( on ps3 push R1 + R2 + L3 to the right) and turn around go under RR Bridge turn around just in front of SS Bulker head back full throttle all the way, dive on sunken barge get another $7500 and repeat process at high speed both ways.

[Saint_Dyn]

You can make $25,000 a ever 5 seconds if you go to the underwater briefcase.