Are airliners' pilots trained to safely ditch an aircraft? After reading this question and these two answers it is clear that ditching is taken into account, at least for biggest airliners (and with reasons as it occured several times in aviation history).

Pilots are trained to face many technical problems that may lead to an accident (engine flame-out, cabin fire, partial loss of hydraulic power, partial loss of flight computers,...).

But, many airlines pilots do not posses the qualification (nor the training) to pilot specific categories of aircraft such as fighters, gliders or seaplanes. Thus it makes sense to assume they are not trained to fly in formation or land on water.

Is an airliners' pilot trained to ditch as he is trained to deal with technical emergencies? If not, what is its knowledge of such situation (only theorical, practice once on simulator,...)? Is there differences between country's regulation?
This is a very dated answer now, but for what it's worth, prior to my retirement in 1999 from a U.S. airline, we did ditching scenarios in 747-100/200 sims during initial training and then occasionally during recurrent training. Proper execution included being on-speed for your weight, nose attitude at touchdown (5 degrees up as I remember), aircraft configuration (gear up but I don't remember the flap setting), determination of wave direction if possible, and landing parallel to the wave action. It was a relatively easy scenario for the pilots but a busy scenario for the flight engineer. He had to position valves properly at the right time, including making sure the pressurization outflow valves were closed to prevent fuselage flooding.