Hi Gene. I am not up on the latest and greatest in Dive knives, so I don't think it fair or proper for me to suggest one. I can share some info.
I would look for one tht is easy to maintain. I find that the Titanium pieces don't cut to my standards. The more carbon in the steel, the better the cut, the worst the rust, so mntnce becomes the issue.
You might look into David Boye's Dendritic Cobalt knives or Rob's Talonite. They cut well and don't rust. That would be the direction I would choose first, but cost maybe an issue, and they're really not designed specificaolly for Diving, IMO.
I like the design of Kit's (Carson) Dive knife, but I'm not up on the material.
sal