...i can create the sand effect and beach/land join, but not too sure which way to go to create a realistic sea effect/surf.
The old Beach Landing Board; no problem! There are a number of ways to go about this, so I'll describe it broadly.
Start your water with a paint base. Whatever your taste in water is, paint it; blue, green, brown, your choice. The trick with the paint is to graduate the shading from sand to edge so that the 'water' nearest the sand is lightest and the water out by the board edge is darkest. This creates the illusion of increasing depth moving away from the beach.
Your next step is to make the water shiny. This could be as complicated as pouring epoxy (Envirotex Lite is a favorite around here), brushing on a coat of polyurethane or Future, going nuts with a tube of silicone caulk, or any combination thereof. Many people like silicone for the ability to sculpt little waves, where as epoxy and the ilk create calm waters. I find calm waters easier to game on just because it's flat (good for boat to boat combat), but beaches tend to have waves so...your choice. I have seen people paint a coat of epoxy and after it cures then caulk a few small waves in. Some folks like to tint their water; you probably won't want to since you don't need any depth.
That's the basics. I'd also suggest doing all your painting before gluing sand down just to make things a little easier. If you want crashing, white-water waves, that's a different technique if you want to hear it. Never hurts to paint shark profiles and have fins sticking up out of the water. I mean, if this is a landing beach and soldiers are getting killed in the water, sharks are apt to show up.
On an unrelated note, this site has been moved to www.terragenesis.uk and you can find all the regulars there with more helpful advice. I am the nightwatchman here while the move is completed. I'll be around if you want to hear more from me.