sounds to me that the ESC is actually ok, just the drive train is stuck
1/ disconnect the motor from the shaft.
2/ remove the propeller from the shaft
3/ remove any nuts from the propeller shaft,
this should then render the propeller shaft free.
4/ try to spin the motor using the ESC, if it spools up, thats good.
5/ try to hand turn the prop shaft.
if it turns freely, re connect the motor to the shaft, but be careful that any lock nut goes up against the coupling, NOT the prop shaft! once that is done, tighten the locknut against the shaft as TIGHT as you can. then, put the washer on the prop end, followed by the nut, followed by the propeller, then screw the lock nut up TIGHT against the propeller.
IF the propshaft is jammed solid, heat it up to melt the epoxy and remove it from the boat and replace it