Make sure your "Gator Tales" caption is in its own group. Select the group (NOT the caption layer), and at the point where the caption is at its lowest position (i.e. supposedly underwater), draw a rectangle mask around the caption and set it to "Subtract". Your caption will disappear. When you play the project, though, the caption will move up from behind the mask as if it's appearing out of the water.
You'll want to add a bit of feathering to the mask to soften the edge, and then you can think about refining it further with reflections and that sort of thing.