I realized I could trim this into buoys without having to use power tools. I held the piece firmly with one hand, and sliced the rest with just a bread knife. I cut them into rectangular blocks and trimmed the ends afterwards.
I poked some skewers for handles (which made it easier to paint the buoys) and primed the buoys. This top photo shows them drying.
Trim and pant the buoy handles. Add an eye hook and run some twine through and voila!