It's easy. My canoe polo team mates and I built 7 polo boats from one mold in one week. We used polyester resin, the mold was well used and had a few defects, but hey, the boats are still in service after nine seasons of polo.
No gel coat, so they are clear. We put chopped reflective plastic wrapping paper in a couple of boats to good effect.
tomorrow I will try and post a pic.
If you have to make a mold though, you have much more work to do. 1st make a plug, or replica kayak, or slightly easier, borrow a boat that you can coat in mold release to make a female mold. The mold has to be mirror finished gel coat, Every defect in a mold will show in what comes out of it.
Canoe polo is great fun! Good luck with the project.
Mike Moss