Gap Filler and Light Conduit Sealer Hand moldable rubber gap filler can be applied underwater without messy caulk guns or mixing. Butyl Tape Retains a flexible, tacky consistency making it well suited for a variety of permanent or temporary leak stopping applications. -Pack around light cable to seal or prevent leaking pool light conduit -Replace rubber gaskets with or without out removing fitting -Fill and seal cracks, gaps or voids -Use under pool putty for pipe repairs