Is a Titanium knife better than a stainless steel knife for spearfishing and diving?
Titanium knife pros: The biggest pro for titanium knives is that they are more corrosion resistant than steel, but not so much than good stainless steel. This is useful for divers, who will carry the knife of long periods of time in highly corrosive ocean water. Another pro is that titanium is lighter than steel. Reducing weight can help reduce strain during knife use. It is also good for applications where every ounce is important such as backpacking. Titanium is also harder. This makes it less likely to ding and dent during use or storage.
Titanium knife cons: Titanium is significantly more expensive than stainless steel. It is a rarer metal, and the price shows it. For those concerned about price or value, this might be a deal breaker. While harder, titanium is more brittle than steel. This means it is more likely to break. A titanium knife will not be good for prying or anything that will put sheer force on the blade. It also does not keep an edge as well as steel and will need to be sharpened more often.
One of the main uses I put the spearfishing knife to is free a shaft that get stuck in the reef. I use the knife to jab and chip the hard coral rock around the tip of the shaft to make more space for the flopper to be extracted. The knife blade cannot be brittle for this task. For this reason alone I would not choose a Titanium knife for my kit. A good spearfishing knife is the Speardiver Skene Spearfishing Knife, it's low profile, single piece stainless steel that's very hard, durable and maintains an edge.