Building Pontoon Paddleboat Would Screw-cap Bottles Make A Good Buoyancy Agent For A Pontoon?

Would screw-cap bottles make a good buoyancy agent for a pontoon? - building pontoon paddleboat

I intend to build a pontoon with PVC pipes, the ends butt end, I've optimized hydrodynamic piece. To ensure this is kept permanently afloat in the port for sea water, I thought of packing with insert screws into plastic bottles.
Does this work?