Picking a dive knife? Blunt or sharp tip?

Get a cheap knife. You will end up losing it. It seems the easier it is to get out of the sheath the easier it comes out when you do not even realize it. I would rather replace a $20 knife than an $80+ knife anytime.
I no longer wear a knife on my leg. Got tired of it catching the kelp. When I do wear a knife it is a very slim lined, sharp point I can attach to my left forearm. On ebay for about $11. Works great.

FWIW, I wear a knife on my PFD, butt down/quick draw just for in the water survival in case of a tangle after dumping. 

Pat