[SIKSUKR]

I happen to be looking at our styro production plant as I write this.We manufacture EPS(expanded poystryrene) which is what BT is refering to.White bead styro like that which is used in Styro coolers and different packaging.It should never be used for flotation in a "raw" state.It degrades pretty quickly from uv and it will always continue to flake off.Most stryo that is used for flotation is extruded polystyrene(closed cell) which stands up much better.These buns are usually pink or blue.

NB,we sell to big marinas that do use our EPS but concrete is cast around it.And as Aqua pointed out it can have a rigid PE exterior also.But in his case I think that they are filled with an expanding spray foam like urethane.