I think you should also consider the issue of spearfishing near a public beach with plenty of kids swimming...If your kids are shooting fish, sooner or later they will attract a shark. I question if it is "RIGHT" to allow a behavior that could bring a shark in, especially if it is going crazy over the vibrations from a speared fish. The kids in the water, have a right to be swimming at the beach, without someone potentially causing them to be attacked.
If your kids can spearfish off a beach there are no swimmers at, and you have taught them well about not pointing the guns at each other, and what fish species to shoot, etc., then this sounds like a great plan, to me.
I only mention the spearfishing off of swimming beaches , because this DOES happen here in Florida, and it DOES cause problems sometimes....There used to be tons of cuda off the rocks on the Palm Beach inlet, and a bunch of freedivers started shooting the cuda to sell for catfood....they shot many hundreds, and in the process, often brought 10 and 12 foot bullsharks to within less than 100 feet of a swimming beach, with kids in it ( by the pumphouse).
Fortunately, I know of no attacks that occurred, but this is dumb luck
