The OEM FCTM's have sections on ditching procedures which are fairly generic. Simulator sessions for ditching is not part of the training matrix for airlines as a general rule. In the military ditching drills were practiced routinely, in the simulator and aircraft. Don't recommend doing it in the aircraft, memorably the NATOPS Section 5 procedure had a number of cautions and warnings in the procedure. One particular warning was don't ditch if lateral control is compromised. Another warning was don't conduct ditching practices with an engine shut down. Having seen the blue on the wrong side of the plane at 4,000', against objections to the driver, I would consider that an understatement. The problem with an asymmetric case ditching practice is not the ditching, it is the recovery/go-around, where the pilot may have a fist full of thrust levers that are not symmetrical when he pushes them forward. As the ditching speed can be close to VMCA1 and well below VMCA2, then things can get interesting rapidly. (difficult to get a Wing CO to accept the warnings of a FNG 40 years ago...).
Ethiopians B767 swim at the Comoros was a controlled crash against all odds, with the hijacker hitting the captain about the head with the axe as he ditched the aircraft. Impacting wings level is evidently worth while, at the correct ditch speed. The ditch speed is usually minimum energy state, but that may not always be the case, geometry may require a slightly higher speed. The captain was heroic in his actions.
An OEM/regulator study done on the survival time following inflight cabin fires supports the fact that a ditching at any time over water is a possibility however remote the chance of a cabin fire may be; if there is a cabin fire, and it cannot be put out, the survival time is unlikely to stretch to an airport arrival.
Tin hat on... years ago, after passing by a red team ship that was happily plinking the sonobuys we were placing in the way of a boomer transiting in shallow water, we got a call of smoke in the cabin, looked back couldn't see the tac crew. Guys hit the smoking cabinet that was sprouting flames and smoke with a large dose of BCF, and continued for a really long time (felt like days, was less than a minute) In the interim, nav gave nearest divert as about an hour, and I prepared the crew for a possible ditch alongside the guys shooting out the sonobouys. Fire went out, so we moseyed back home once the risk was removed, crew off masks etc. A non event, however, one of the guys woke up the next day with a new top of grey hair, gained overnight. Smoking is bad for your health apparently.