Huntsman 31 is pretty much the only model I could come up with that is easy to build with 2 motors, although most of the complete kits seem to come with just one set of running gear. Thanks for the link, it gives me another source for a kit.
Yes, 2 separate ESCs and batteries would be needed, as one stalled motor would "kill" the other if only one ESC was used.
Our lake is concrete, but hasn't been properly cleaned out for quite a few years. It was built originally as a boating lake, but has become very popular with swans, ducks and geese. Not sure whether the lack of cleaning is to encourage the birds, or because the town council can't afford to do it.
The "weed" that disabled my tug was very fine, like green hair. It wrapped around the the end of the propshaft, getting between the washers and the end of the tube - just like what happened when a Scalextric track was set up on carpet, and hairs got wrapped around the axles. Shaft was jammed solid, but the motor was still whirring away because it's fitted with an O-ring reduction drive. The drive belt was just slipping. I guess that saved a blown fuse (or worse).
Not sure that any kind of guard would deflect this kind of weed?
Fortunately another club member managed to nudge my boat back to shore - tug being recovered by a cabin cruiser.