In reply to jmerrick21:
I've had an Olympus TG (the older TG4)for a few years. There are two macro light options: the FD-1 (which I have) which is a simple diffuser for the built in flash and can be used underwater; and the LG-1 which seems to use fibre optics to guide the light from an LED on the camera into a ring light and can't be used underwater. This is all on the Olympus website.
Like the others, I can't see how any of these effect the actual camera's waterproofness.
By the way, I found the decorative ring around the lens can come off and I managed to lose that underwater. Worth removing it first, I think - it is necessary to remove it anyway to properly rinse and dry the camera after use, especially important in salt water.