consider an air-horn as a possible alternative... potentially more debilitating than mace or wasp spray... (think about someone blasting 3 bursts directly in your face) certainly creates an element of surprise and lets everyone in the vicinity that something is up... an air-horn can accomplish multiple things at the same time... surprise-scare-debilitate-and alert those in the area... and you can pick it up at the boat shop... Safe travels!