Usually, the ESC senses when it is getting a bit too warm for comfort and reduces power delivery. Blowing a fuse does leave the boat drifting, but without a motor fuse, using a bit of good sense and gentle reversing can unwind what has been picked up, entirely if you are lucky, enough to limp in if not quite as lucky. Of course, if its a bit of discarded fishing line thats been snagged, the boat might be effectively anchored.
The purpose of the battery fuse is to protect the boat from misbehavior in the ESC.
On Stanley Park, you do need another boat for rescue - it is surprisingly deep in places, and much of the bank is inaccessible. A mate of mine once claimed to have cured some warts on his hand after trailing said hand in the water while his girl friend was rowing him. Down at Fairhaven, we have been pretty much weed free the last few years, its a "no fishing" lake so relatively few lines left, just feathers at moulting time of year.