Ok, got something working. No way I'm going to be able to finish this but at least i'm happy with the idea.

Sonar scan is working. Can you spot the tire in the scan?

The idea is that you can use the sonar to scan the ocean floor, and then you have to go back over things and hit a button to collect them (or just scan them) and the goal is to collect at least one of all the categories, e.g. tire, barrel, whalefall, clamshell, atlantis, etc..