Hull reinforcement modules for the PRAWN and Seamoth will NOT protect from creature attacks, just collision with the terrain. Or if you crash into a creature, I suppose. It will not defend your Seamoth or PRAWN from being attacked by a reaper, boneshark, ampeel, or any other fauna. The only thing it does is lessen collision damage, and collision damage only, for the seamoth by 50% for one, and for each consecutive hull reinforcement there is diminishing returns, making it impossible to get complete collision damage immunity. Feel free to test this if you want, get your PRAWN or Seamoth with no upgrades and get a reaper to chew on it, and do it a few times to get an average, then fill the upgrades with hull reinforcements and do the same thing a few times to get an average, and they should be about the same. They may be a few damage different, as the damage applied is usually pretty random, but it's safe to say they should be pretty close on average, with or without hull reinforcements. Have a good day (: