Well, if it is just a "hero" droplet, I would try blend-shapes.
So as it hits the water, you can blend to a psuedo-squashed version of the drop geometry, then you can also make the "hero" drop an emitter for other smaller instanced/animated droplets that break off of the main droplet on impact.
Also, there are also a few GREAT melscripts on Highend that will help you achive the "drop" look on the plane if that might be what you are trying to achive.
(for the "expanding-rings" stuff IF you need that)
Israel "Izzy" Long
Motion and Title Design for Broadcast-Film-DS