http://en.wikipedia.org/wiki/Cocaine_Cowboys is a good documentary on the drug trade that has an interesting portion on the use of submersibles in the drug trade. That documentary came out in 2006 and it showed how drug runners had already evolved past these vessels by using containers shaped like driftwood logs and attaching them by long ropes to fishing vessels. The driftwood containers had gps trackers on them so when the coastguard came close they would sink them with the rope attached and another ship would pick them up later. I think its available on thepiratebay.
You don't even need GPS trackers on the containers. Just note the GPS location at the time you cut the rope. Have a transponder aboard that listens for a specific signal before it starts transmitting. Such devices would be cheap to make and might be harder to detect than GPS devices which broadcast location signals.
