Hi again Sonar,
A Springer is a great idea, a good fun, almost indestructable boat, cheap to make with real basic hardware plus the scope to make it into anything you like, even perhaps a 'Minesweeper' Springer. Type Springer tug into google and browse....Cost about £2.00 for the hull out of a bit of plywood, £6.00 for a motor, £20.00 speed controller and a 7.2v Buggy battery,plus the radio.
Cheers.........Ron.
PS. Grandad was on Minesweepers in and around the Solent in WW1 and 2. I lived on IOW with them in my youth....love it, even if they say their schools are Cr....P!