It has been alluded to, but not said that I've seen, so I will: the right thing to do in a ditching depends greatly on what you are flying!
There is a world of difference between a 206 on skids that wandered too far from shore (or is looking at a river) and a 225 80nm offshore in the North Sea.
There is almost as much difference in the 'fidelity' of the various HUET dunkers out there. Survival Systems of Dartmouth, NS, Canada has an incredible setup, for instance, that simulates all the worst ocean weather, helicopter cabin/cockpits, window types, and roll-over/sink scenarios. Others are just a box that flips over with doors, etc that can most generously be described as generic. The former is what militaries will use (pay for) whereas on the civil side I've found I'm more likely to be subjected to the latter.
Before you fly close to water, ask yourself about floats, door jettisons, windows, location of survival equipment, life jackets, and so on. Don't forget weather, season, temperatures, clothing.....
If you are going to land on the water, there will be differences between:
1. CFIT/W
2. Auto/OEI class 3
3. Land immediately
4. Land as soon as possible
5. Lots of time but no choice (ie fuel leak)
Personally, I would be very surprised if any helicopter without floats stayed anywhere near vertical once in the water unless held there under power. I agree to hold the rotor clear of the water as long as possible (minimum rpm).
I am envious of the waterbird time many 61 drivers have had.
Based on my own unfortunate experience I can offer the following observations:
1. You will react the way you have trained/planned. Do it right.
2. If the rotor hits the water at full RPM, there is nothing gentle about the result.
3. If the tail rotor hits the water under power, same thing.
4. If you think your cockpit is uncluttered, take a closer look. Every one of those pieces of [vital] kit will be in the way at the wrong time.
5. Wear what you need, gear that is safely tucked away likely won't make it out with you.
Just as the decisions that wind up putting you in the water were made long before you get wet, how you handle it and whether you survive will have been decided just as long ago. Be prepared.