OK, I put my weight belt on so I would stay on the bottom long enough to see if the food coloring got sucked into the dimple anywhere and it didn't. The food coloring just hovered there for a very short instant, then dissipated on out into the water. I was very, very still. I did this three times (which was a great workout for my lungs!) and I just couldn't see where it might be getting sucked down into the dimple.
So we're confused as to how we could have a perfectly round dimple, about the size of a third of a softball pushed down into the floor, but no apparent leak there. And as I ran my foot along the bottom out from the dimple, I feel a sunken "trench", albeit small. This is an area that is supposed to have solid Happy Bottom. I watched them install it, so I know it's there! Does this sound like a pinhole, ground cracks (our yard is really bad right now) or possibly ant damage?
Any suggestions/help? Thanks.