Yes, helicopter pilots can fall victim too. It's best to approach where the shoreline, or other objects in calm water can be used for reference as to altitude. Once you're close to the water, the downwash will give you a reference, as you enter a hover. It's spooky though, as while in the hover, the downwash will be moving away from you in all directions, so if you look at the surface in one spot, you'll have the sense that you are moving, when you might not be.
When you finally land a helicopter in the water (float equipped), it's unlike other landings, as if you don't actually watch your contact with the water, it may be hard to know that you're "down". My first time, I had the collective bottomed as I realized that I had landed, because there is no feeling of contact, as there would be with skids on the ground, or a floatplane/flying boat on the water.