I’ve been making kayak trolleys for a few years now and lots of people use them instead of driving their kayak to the water on a car, but the increasingly popular vessel of choice is the stand up paddleboard (SUP). They are flat on the bottom so don’t sit well on a kayak trolley, and are generally much bigger than a surfboard, so hard to just tuck under your arm or mount on a rack at the side of your bike like this resulting in many unnecessary car trips out to the beach, even if you are relatively close by.
My latest creation is a variation on my kayak trolley with flat bars suitable for strapping a SUP onto. I took it for a test drive in a very vigorous easterly wind, up & down a hill and over a few bumps and it handled very well. There is space to strap some gear under the board in front of the wheels. For more info look here.