Good questions. Re: the duct tape... It provides a secure method of attaching the thrusters/suction to the PVC pipe on either end without disrupting flow dynamics. Since it is waterproof, I think it will have a long lifetime, but is also easily replaced at $0.
The magnet serves a triple...
I knew I would get a variety of responses, but I traded cosmetics for functionality. Find me a drone with a suction dredge and capture basket. I'm ready for the the Treasure Coast.!