We folding kayak paddlers use inflatable flotation bags in the bow and stern, which serve the same function as bulkheads in excluding water and maintaining buoyancy. Plus folders have inflatable sponsons along the sides that provide both rigidity and flotation. People have crossed the Atlantic Ocean in folding sea kayaks from Klepper and Feathercraft – they are in some ways more seaworthy than rigid kayaks especially in rough waters. I know someone who uses a Feathercraft folder on research expeditions in the ice filled waters of Antarctica. I bought one of the Pakboats I’ve owned from a guy who uses their folding kayaks and canoes on his guided fishing trips to Alaska and Patagonia. Special Forces in many countries use folding kayaks for covert marine operations.
I have found that folders are easier to climb back into than rigid boats because they are so buoyant and many models can even be rolled, as you can see on the video I linked you to.
Also, I have landed on or bounced off lots of sharp rocks – people unfamiliar with folders don’t realize how tough they are. The hulls are reinforced with additional rubber – even if they somehow get torn or punctured, they can be patched in the field, even in the water (I carry a special kind of tape that works for this). And if the boat has flotation bags and a sea sock, you can continue to paddle even with a hole in it. A sea sock is a waterproof nylon bag that attaches around your kayak coaming and encloses your legs and feet – it adds warmth and keeps water coming into the cockpit from flooding the hull – I only use one when I have gear bags instead of flotation bags under the deck.
In 14 years of paddling folding kayaks, from the Atlantic to the Pacific, in coastal waters, rivers with industrial shorelines (concrete, protruding re-bar, submerged metal junk), all sizes of lakes and even rocky streams and moderate whitewater, I have NEVER had a puncture or tear. Because they are flexible they tend to bounce off or slide over obstacles.
Skin on frame boats are similarly tough. My skin on frame has a two-part polyurethane coating on 9 ounce nylon ballistic cloth…like what is used in protective military gear. I can hit the skin with the claw end of a hammer and it just bounces off. There are YouTube videos where people try to damage the skin on one with all kinds of tools.
By the way, a fiberglass boat can get really trashed on rocks – they can be patched, of course, but they are not the best choice for rocky waters and are not all that much lighter than plastic rotomolded boats. There are light composites around 14’, like the beautiful boats made by Stellar, but those exceed your budget. You might be able to find a used one, but even used those are pricey.
Inevitably, the choice is up to you. but don’t rule out folders because you believe they have limitations which they do not. It’s a shame that there are so few opportunities for people to see and test folders because they really are remarkable boats.