Thill makes a plastic float with replacable LED battery/light assemblies in the top. Very bright and replacement lights are readily available.

You can also put a small light stick on top of your own floats. Clear water resistant athletic tape works to secure it for a few hours. Silly string (the elastic stuff for herring wrapping a kwikfish) also works but is a pain to use.

Am working on a design for a GOOD LED powered float. Will post when the final prototype is completed smile