Paddles - forget it
Last winter I had the unenviable pleasure of swimming/wading about 3/4 mile around the edge of a reservoir towing a rib (not mine) when the battery failed.
Sadly I had the drysuit on so I got volunteered.
No tide (it's a lake remember) - 10 knots of breeze, 5m Humber, big wooden paddles, 15 stone reasonably fit dad, 12 stone karate black belt, rugby playing 15 year old...........
Couldn't move it an inch!
Morals of story....either get an auxiliary (with pull start), or make sure that there are two ribs out at all times.
Oh and get a new drysuit so I can give mine to son so he can swim next time!
Tax is paid by mortals