Spent the day playing around with rendering and materials. This time I used Vray instead of Mental Ray. I must say I'm rather pleased with how the water turned out, particularly in the second shot (as usual, click the images to see the full-size versions). It does take a while to render though (just over an hour for the second shot and I believe about 15-30 minutes for the first one). The only problem is that this is about as large as I can make the scene, since larger ones quickly exhaust the 2GB of RAM I have and subsequently bring my computer to its knees. Maybe I should start looking into getting a new one.
UPDATE: Looks like I spoke too soon. I tried rendering a scene of 640x640 blocks again (the first two are 272x272) and this time it worked just fine. Interestingly, this render only took 26 minutes. Guess zooming out helps. This render is also a good illustration of the scale of Sapphire Island. I think Coral Harbor is going to have about the diameter of this entire scene. And since Coral Harbor is only a small part of the island, you can see it's going to be a fairly large project.