Baby Beach was my favorite beach on Aruba. It is a really great beach for children because of its shallow water, but it also has, in my opinion, the best snorkeling available.
It is a small cove, and the water barely gets over 6 feet at the deepest. Most of it is around 3 or 4 feet deep. On the outer edges of the cove, there are tons of fish hidden in the rocks, and you can just float along and watch them. Also, there is one spot where there is a break in the rock, and it opens up into the sea. That is where it gets deep but is also where the best fish are. You see tons of huge angelfish, lots of little black ones whose name I'm not sure of, and a ton of parrotfish, too. I think this is the best beach for beginner snorkelers, but advanced snorkelers will enjoy it too. Also, the fact that you can rent equipment there is a plus.
If I had to rate it out of 10, I would give it an 8--only an 8 because the beach tends to be crowded (not the water--the water is not crowded at all), and you have to pay in order to get beach chairs. Also, the view is marred because there is a factory behind it--see photos. Don't worry; there are no fumes, or they're barely noticeable.