I just want to say that we have yet another talented artist in here!!! Bravo! I try to avoid backgrounds with a passion and have nothing to offer you with regard to advice in drawing water. I do agree with the others that you should experiement with darker tones.
I typically use a mechanical pencil (I think .7 mm HB lead). I use q-tips for blending the first couple layers, then go over the drawing again with the mechanical pencil for fine detail work. I sometimes use 7B, 8B and 9B graphite pencils for some of the really dark tones for the finishing touches. I have a kneaded eraser, but probably don't use it nearly as much as I should. I typically just use the eraser provided on the pencil...lol. I have what's called an ebony pencil, but I very seldom use it. As far as paper goes, I typically like smoother paper and have recently fallen in love with bristol paper which is also thick and less prone to crease lines and wrinkles. Sometimes though, I use a more toothed paper. It all depends on the effect I wish to achieve at the time.
The enhanced image you presented looks really nice and I am sure with a little practice you will master darker tones in no time. Still, I just think the drawing is so lovely as is and I have no doubt the recipient of the drawing will agree. I hope to see more work from you in the future!!!