If you put your finger on the glass and move around, sometimes a curious sea lion will follow it! My wife is the one pointing and she is dressed in white. If you look closely, you can see a partial reflection of her.

Sea Lion Sound (exhibit) walk-through tunnel at the St Louis Zoo.

Nikon D800 w/Nikkor 28-300mm f/3.5-5.6G VR
@28mm, f/11, 1/125s, ISO 560...cropped