Yeah, like others have mentioned; it's currently a Sellers Market, so the hard part is going to be finding a boat....period. But when it comes to "Salt water" the rules are all the same as "fresh water"....the 3 "Cs" apply; Condition, condition and condition. As an example, in a normal market, say..last year, I would sell my boat for $5k. Right now...wouldn't take a penny less than $6-6500 just because that's what the market demands. If you can wait, it will serve you well I assure you.
For an example; I use a 17'6" center console "Bay boat" that runs in 6-7" of water. Has a 90 hp outboard and I'm not scared to take it to the wrecks off Florida's west coast in the Tampa Bay area which are 3-5 miles offshore....but only when the weather and the sea are cooperating. There will be others who tell you they've taken a 16' flats boat from Miami to Bimini Bahamas. Good for them. Not for me, lol. If you really want to go "offshore", where you can't see any land the fish start to bite deeper, then look for a boat with high freeboard. Something below your knees like mine is too small. And even then, the weather places the biggest role. I will never forget a trip we took on a friends, 40' boat w/quad 300hp outboards. Big, fancy, high-dollar and new. We were going to the "Middle Grounds", roughly 70-75 miles off the coast of Clearwater. Left the harbor and the sea was glass, no real issues in the forecast. Got about 18 miles off the coast, and the Sea had a change a heart. That "huge boat" (to me at least) was thrown around like a 12' dinghy. We had waves crashing over the bow that were 4-5' OVER the front rail. Almost lost a friend overboard, but luckily someone caught him right before he went into the drink. The swells were so bad, there's ZERO chance we would've found him. Now this story is not intended to "Scare you", but to let you know that you MUST, 100%, respect saltwater. This isn't a lake. Things happen quick. So before you head out to the deep blue water, make sure you've learned as much as possible.