The hook knife is for emergency situations when you need to untangle yourself from lines. The knife goes straight into the built-in pouch of your spreader bar or harness with no need for an extra pouch. Then it is right there for easy use and in reach when needed. Everyone riding in waves or deeper water should have one of these. Old hook knives can dull or rust over time, especially in the salt water, so check your knife once in a while and replace when necessary.
(product may vary)