I saw this tip on you-tube some while ago. Silicon sealant makes very nice sparkly water and by building up in successive layers can be moulded into waves, ripples, wakes etc. I found I had these pictures from a base I made a while ago (some of you will have seen them before on another site)
First, I sprayed up a piece of hardboard (aka "masonite") with 3 different colours, green and blue.

Then just spread the sealant over - it naturally forms wavelets as you squeeze and draw it out, with a minimum of spreading about you can get this effect:

The spoon can be used for "patting" or drawing up the material to form peaks (splashes), etc.
Then I cut a hole for the models' hull, and added some more sealant to form a wake. I sprinkled a few grains of salt into that too, to approximate foam.

And this is how it looks:

