Different types of boats there. Rivers = smaller, more manoevarable, sea = larger, less manoevarable. I’ve got a P&H Capella, great boat for the money, used it on a canal and lochs but it’s too big and cumbersome for rivers. That said, boats are like climbing boots, you really need to try thek out. Where are you? Sea kayak Oban do weekend paddling trips around Oban where you can trya number of differeent boatds and see what fits you. Glenmore Lodge do the same. If these don’t work for you, there’s bound to be somewhere closer