When I floated up to the spot, a sliver of sand had started to show (as seen in the top image). It was incredible to be in the middle of the ocean with no one else around me... and no sounds other than the ocean and an occasional boat. As the tide continued to drop, the sandbar continued to grow... at its biggest, it's about a half mile in length. However, like anything in the ocean, it's constantly changing... and by the day I left, it had shifted a couple hundred meters to the south.
Surrounding the sandbar are coral reefs... and just outside the reefs, the ocean depth drops rather significantly. This made for some incredible snorkeling! (which is why I brought the snorkel gear) I did some free dives down to the ocean floor and was surrounded by hundreds of colorful fish. It was a pretty rad experience.
In the second image (with sailboat), you can see how shallow the ocean is in this area. During low tide, boats coming to/from the island had to take a much longer route to avoid the reefs. If I had wanted to, I could have walked all the way to where that sailboat was.