Hey man. Saw your post about a gun in Jax. Don't listen to most of these guys. they're all assholes and want to be trolls. Some dudes are good, but 80% of them think they're freaking doctors in diving. I have a buddy that has a brand new JBL that would be good for you, that koah though is a solid price for an awesome gun. Pretty sure the JBL is a 38" or 90cm and he would sell it around $330. They retail for around $380. send him a text 904-671-5090. His name is will. Tell him Chase told you to text him about the JBL.
A good size is 40-46 for scuba here and shorter. Lots of wrecks and ledges so anything super long will get in the way. Viz here isn't amazing either, average is 20-30 feet but laterly its been 50 foot plus. Not sure how familiar you are with the area but if you have any questions let me know. I've been commercial fishing out of here all my life and got into freediving about 3 years ago and started shooting fish. What brought you to Jax? Military?