Look into the Cape Falcon F1 skin on frame kayak. Brian Schulz, the designer/builder, based it on the legendary Mariner Coaster, which was a unique 14’ kayak that was designed to take on rough water but still be good for flatwater speed. Brian started out as a whitewater paddler so he knows how to encorporate versatile performance into the dozens of innovative boats he has generated over the years (and has overseen countless ciinics for those who built their own.
I just bought a lightly used F1 myself this week, after having had my eye on building one for years. Taking it out today for the first time on the water (I had test paddled two others in the past at skills camps).
Skin on frames are actually quite tough and not easily damaged. I have been using them for 23 years in everything from rocky coastlines to Class 2 streams. The skins are often made (like my two wood frame SOFs) of 9 ounce ballistic nylon with a rugged two-part epoxy. You can’t even pierce the stuff with the claw end of a hammer and they will bounce off rocks and even pokey rebar stubs and submerged metal structures,
Walking is great exercise and has one benefit you won’t get from paddling: walking is weight bearing, which aids in bone density retention as we age. Unless you are doing frequent mile long portages between lakes, carrying your kayak or canoe, you won’t get that benefit.
But walking and paddling use different muscle groups and are a great complimentary routine. And both, if done briskly enough to get your heart rate up, are cardio exercise, which is the ONLY way to reduce visceral fat.
I use to do a 3 mile daily walk in an hour or less with a 50# back pack to prepare for hiking into Colorado mountain wilderness areas in the fall. These days my bad knee limits doing that, but I do PT exercises and walking. Not the same amount of joy as when I paddle.
I had one about 8 months ago, and I’m now bicycling about 20 miles a day. I’m very happy with mine. Although, I still have a mental block about letting it rip on mountain bike trails.
I don’t agree that kayaking doesn’t provide the physical intensity for a cardio workout. That depends on your paddling technique. Perhaps your fitness level is already relatively high, but managing to exceed your aerobic capacity is just a matter of pushing harder. The closer you get to the theoretical hull speed of the boat, the exponentially harder it is to increase speed. Try increasing cadence. That should peak your aerobic threshold.