The scuba part is the wild card. It takes a special knife, imo, to be "good" for scuba diving. Most knives, even carbon, can stand some underwater time if you're good about tuf-clothing them off to prevent rust. To withstand prolonged underwater time, however, and to withstand the abuse that a scuba knife is put through, is another thing. I'm inclined to recommend 1 knife for survival, and a different knife for scuba. I just picked up an Oceanmaster Beta Titanium dive knife, and that is one AWESOME scuba knife. Their proprietary beta titanium formula is light years ahead of regular titanium, which is known to be brittle.
As far as a survival knife goes. To someone who has very little criteria for what they want and what they need, I have a few tried and trues I like to recommend. For a do-it-all type knife, I like a 5-6" blade. Some here like smaller, some like bigger, so YMMV:
These range in price from $50ish to $200ish
Ka-Bar Gen II (I personally don't like these, but they work)
Ranger RD6
Fallkniven S1
Rat RC6
Stick around for a bit, you will get LOTS of options. If you could tell us more about yourself that would help quite a bit:
What's your camping/hiking/survival background? Done much? Just getting started?
What knives have you used in the past? Likes? Dislikes?
Are you prone to military-type tactical knives, or woodsman-type traditional knives?
Price range?
Experience with knives as far as maintenance, sharpening, etc...?
Do you carry any other tools with you when you camp? Swiss army knife? Axe?
Those should get us started