Catch the Seashell
Find this one just outside downtown Lemuria- you'll hear the gameshow host hawking his brainchild.
Activate the lazer maze inside to start things off.
Then smash the large brown treasure chest outside, next to the host, to build a marvel vent below the bubble.
Enter the vent to start the show.
The goal is easy- swim into seashells, avoid starfish. The only tricky thing here is depth- if you're swimming into a shell but not getting it, try swimming to or away from the camera a bit.
Rack up at least 20 shells to win a brick, and get a point in the Minigame Master challenge.