I forgot about that oil rig. That's an elaborate one. Thanks for the link/reminder and nice comments. Yeah, I think someone else thought it was an April Fools joke too. Nope. Still working on this.
Did some more testing and found a few more problems today. Ug. Testing is lame. Just swimming around is more fun.
After some thought, I figure it would be best to have a normal sized pond but one that is invisible to attachTo. Originally I wanted one that I could just fit inside my unit's body. And I guess I'd still like to have that ultimately. But the benefit of the larger pond is that anyone who is near me will dive with me. As long as they don't swim too far away from me, beyond the edge of the pond, they will stay at the same level as me. Is there a way to set something invisible in the game, but still have it present?