Aside from the truth that ditching is extremely rare, a couple of misconceptions are above.

Ditchings are indeed survivable and it is not true that the aircraft will breakup upon contact. The ditching of USAir 1549 in the Hudson neatly refutes that. Wikipedia has a list of ditchings, some of "modern jets" in which a good number of people have survived.

All TATL aircraft carry very large rafts, capable of carrying 50 or more people. Enough are on board to accommodate all passengers and crew. They also carry survival kits appropriate to the route and time of year (I'll leave it to you to guess what is carried in those). Emergency locator transmitters are in each raft and even if some failed there would still be enough to light up satellites overhead.

The purpose of the live vest is to support you at the surface while you make your way to and board a life raft. Accomplish that quickly enough and no hypothermia.

And yes, almost all passenger aircraft are tail heavy and rear emergency exits are not to be used after a ditching.