For both of these, you need two different things.
For your first problem/question, you know how you can select water material, change its width and length? Well, you can also change the depth, that's the middle set of numbers. If you change it to a specific height, it'll only go down so far, and you'll be able to create the pocket.
For your second one, go into object maker. Go to the second tab, and you should be able to create a sphere, or block of water. Well, I don't really remember which tab it is, but if you mess around with the object maker and find the sphere or box, you'll be able to add it as a water object, thus creating only a small area of water. (However you can also try the previous information to do the same thing.)