What is a blunt-tip dive knife?

Answer 1

Many dive knives have blunt (squared-off) tips. This makes them safer. You're not likely to need a sharp-tipped knife underwater. You're more likely to just need the cutting edge. Sharp tipped knives tent to snap off and break when prying at things. The blunted tip is more practical as you never need to stab anything but you often need to pry things underwater.

A sharp knife is what you need for cutting line and old netting etc.