Suggest a waterproofing adhesive for reasembly of GoPro5 black housing

Disassembly and Reassembly was actually a success and I managed to salvage a GoPro 5 Black that spent quite a while tumbling around in a sandy Hawaiian beach break. So much fine sand worked its way into the housing that the (tiny) grounding spring was completely fouled resulting in no power up or charging. Once cleaned and reassembled it operates normally. It is however, no longer waterproof. Can you recommend a suitable adhesive/sealant for the face plate/cover? By the way, Thank You so much for the wonderful teardown and repair guides.