TIMING: post-merge (invididual)
# OF PLAYERS: any, but a smaller number is probably better (e.g. final 5)
CONCEPT: Survivor has done many kinds of mazes before... blindfolded mazes (Amazon, etc.), vertical mazes (Vanuatu), and even mazes with obstacles in them (All-Stars.) But Survivor has never done an underwater maze before!
This maze is done in shallow water. Tribe members can stand up an orient themselves. They can see where the checkpoints they need to reach are. But they cannot see where the paths lie in the maze, and which ones are the correct ones to follow, unless they dive into the water. So they will hop in and out of the water, racing to be the first person to complete the maze. There can also be a word to create at the end, like in the maze in Vanuatu.
This is what the underwater maze looks like in more detail. The players go from square to square, going underneath each divider.
To make the challenge more physical, there can also be some portions of the maze where you need to swim in the water for a certain distance before you can come out of the water (as shown below.)
Also, you can have the tribe members drag a small chest across the maze to make it more physical.