Once you boat batteries are submerged you will have no power to inflate your raft.
I think you would be much better off getting a good inflatable tender that you can tow.
ISPA Yachtmaster Offshore Instructor Evaluator
Sail Canada Advanced Cruising Instructor
IYT Yachtmaster Coastal Instructor
ASA 201, 203, 204, 205, 206, 214
As I sail, I praise God, and care not. (Luke Foxe)