From memory as a waterbird instructor:
Normally, you won't have time to do anything else but land as gently as possible at the bottom of your engine off, in a single. Any thought about landing cross swell, etc will not be an option because you won't be able to time the moment of impact!
With a twin, unless it is fuel contam when both engines stop, you'll have time to consider most of the variables.
Aim of the game is to reduce touch down speed to a minimum! Everything else is secondary.
Picking your touch down point to be across swell is by far the best. never attempt to land into or behind the swell, you'll lose all semblance of control.
IF you have the wherewithall then consider tail first to cushion the landing - but this can be a harsh option if you are able to land with little or no fwd speed where you can simply 'plonk' it onto the water, almost vertically.
There are some schools of thought about putting the advancing blades in first so as to encourage the MGB to depart aft should it feel like it!! [opposite and equal reaction]. But one needs to remember that this action could deposit the MGB in the crew cabin aft too!!
Of course any fancy manouevres need only be considered in a sea state 3 and above. Below this, simply flare it to a full stop immediately above the relatively calm sea and overpitch vertically.
Get rid of as many emergency exits, JUST PRIOR TO ENTRY, any earlier and they could go thru the main / tail rotors and spoil your perceived flight path! Relying on emergency doors after entry into the water is dodgy to say the least because you may have buckled the airframe and the doors may jam.
Once on the water, and in a sea state >2, expect a blade tip strike and consequent roll over due to swell.
ALWAYS attempt to land as close as possible to the wind direction accepting cross swell landings.
DO HUET often and pay close attention to what the instructors tell you. A HUET course in the Uk is only £180/person and worth its weight in gold.