0.6mm Nozzle, 0.2-24 layer height, PETG or other strong material.
I printed this at 0.32mm layer height with a 0.6mm nozzle for strength and layer adhesion, however, I would actually recommend printing this with a bit smaller layer height to decrease the amount of support necessary underneath and to maintain proper roundness.
I printed this with the rounded sides down to minimize support material, and have layers running the length of the print where force will be exerted against.
PETG was the filament of choice as this needs to endure a decent bit of force and sitting outside in the sun every so often. PLA is not recommended unless you keep your pool supplies in proper containers 95% of the time.