Hello there! Upon rereading and looking at Firearms and Naval Weapons, I never explicitly stated if these were 'exotic' weapons, or if they were covered under Martial or Simple weapon proficiency!
The assumption in my head was no, because they are inherently more powerful than traditional martial weapons! Although if you're a based DM and know that martials unfortunately are less powerful than casters most of the time and just give proficiency to everybody, I wanted to ensure there was a way to get proficiency in these weapons alongside unlocking some new playstyles for those that want to invest more heavily into pirate-styled fighting!
And so I give you 6 new Seafaring feats (one of which that piggybacks on the Waverider statblocks!)