If the repair is on a flat area where you can glue a patch over then you may be able to useĀ Selleys All Fix Multi Grip. MultiGrip is a solvent-based glue often used for repairs to vinyl swimming pools and should be suitable as long as the Kayak is PVC or Vinyl. If the repair is along a seam or weld in the plastic you may not be able to achieve a successful or lasting repair and may need to seek out someone who specialises in repairs to inflatable boats.