I have done quite a bit of single engine overwater flying (mostly warm water) so I have thought a bit about it. Most of the recent trips have been in a C172 3 up.
We decided not to bother with a liferaft. None of us are spring chickens so the possibility of getting in to it was going to be slim.
We of course had lifejackets and an ELT. We should probably have taken dye as well.
The most important thing was a serious discussion about egress. In a C172 the seat has to be forward for the rear seat passenger to leave and rearward for the front seaters. Therefore the rear seaters must leave first as they can't reach the seat adjustor. Furthermore, if the aircraft remains upright, in fact even if it doesn't, it will float substantially nose down. How will that affect moving the seat rearwards? Annother difficulty is on old C172s the seatbacks would fold nearly flat. Not so on the newer ones.
Now the single door on the Pipers doesn't seem so much of a problem.
D.O.