Another trap with water landings is judging your height above the surface, especially on flat glassy surfaces. In this case extra speed might be a good idea with a flare slightly higher and gentle descent as speed washes off to touch down. Once you start making contact firm backpressure as it slows will minimise the chance of flipping, ie don't relax until it stops.
1. Speed is not your friend landing on water, especially when the water is glassy. Even a clean floating hull wants to suck its nose down on glass.
2. It is just about impossible to judge your height above pure glassy water. If you can put the sun in the right position you may be able to use the shadow of the aircraft to judge your height. If there are objects floating on the surface or an adjacent shoreline you can use those to help judge height too. Some very experienced float pilots use the trim change as they enter ground effect to know when to flare when flying into very small glassy lakes. Accurate height judgement even on textured water is a skill that takes a long time to develop.
My advice, ditch whilst you still have power if you can so you can set up a very slow rate of descent with a high nose attitude - that way it doesn't matter if you judge the height wrong. Without power there is a lot to be said for flying at minimum sink speed and not attempting a flare - a high flare followed by a stall is not going to be pretty. And in case it goes badly make sure you know how to open the door and exit the aircraft without losing orientation - this needs to be done before departure, preferably on a HUET course.