Segment 1: Stargate Blue Hole. In a remote part of Andros Island in the Bahamas, a deep crack in the ground leads into a beautiful and stunning underwater cave system. Jonathan joins a veteran cave explorer to plumb the crystal clear water in the depths of Stargate Blue Hole. Segment 2: Sponges. A sponge might not look like much, but these simple animals with no brain or ability to move have lived on Earth for hundreds of millions of years. They can hunt prey and spawn, and Jonathan demonstrates how in this fascinating segment!