Hey Macrohead,
This was for a teardrop, but good for water droplet.
CC Blobbylize (referencing a white teardrops on Black Background), with Radial Shadow.
You need three layers.
Dup the Apple image layer.
Above the two Image layers:
Make a new white Solid, create a mask on that solid the shape of your water drop.
Now animate the Mask Shape to get the flow of the teardrop.
You can double click the mask points to change the Mask Shape over time (it’s like Transform in Photoshop),
as it grows and flows, and/or animate points on the mask individually. Feather the mask to about 5 or so.
Precompose this layer, Layer>Precompose, move all attributes.
This precomped layer is above the two Image layers, turn off its eyeball.
Here’s the waterdrop:
In the Image layer, second down:
Effect>Distort>Blobbylize:
Blob Layer: Layer 1 (your Animated Tear Shape)
Property: Alpha
Softness: Lower a bit, maybe 10
Light>Light Intensity: Up to 300 or to taste
Light Height and Direction:To taste to fit your Scene Lighting.
And for a little more depth, Effect>Perspective>Drop Shadow (tweak to taste)