Go Pro speargun mount and maintenance

   Hola free divers, just borrowed my daughters Go Pro Hero 3. Ready to mount it on my spear gun and give it a ride. She dropped off a few mounts, but can anyone show me a picture of how you have it mounted?

 And what about the seals? I want to grease up the seals before I start. Any special dive grease? Any thing else I am forgetting? Thanks in advance, Ron