Rockjaws are mostly an annoyance due to their high health and damage, and even upon being killed their loot is mediocre.
I was thinking that they could drop their jaws as an item. Said item would be required to craft an upgrade for the boat similar to upgrades for the mast, making the boat able to destroy Sea Stacks, mine Salt Formations and damage Sea Weeds and other mobs by impact without creating leaks on the boat, leaks can still happen through other means like Cookie Cutters and Sea Weed projectiles.