text: Or, contaminate the gunpowder/gunbarrels. Either introducing flaws in the barrels, or some higher power explosive sprinkled into the mix, would result in the guns exploding during training or battle. A tight beam tiny lazer could probably be fired from underwater (just need the right color) to introduce the microscopic barrel flaws. Maybe right around the new barrel modifications :)
  These ships will have inexperienced crews of men who probably can’t swim. They are using new ship designs, guns and new sail plans. Would anyone be surprised if they had a very very high rate of ships lost with all hands during storms/training?
  If he is going to start fires…A small fire near the magazine would not leave most of the crew alive to start complaining about magically starting fires.