You shouldn't take something that isn't yours, especially a divers speargun.
It's bad enough when you lose a nice fish to a shark when spearfishing. It's even worse when you lose your speargun and a fish to a hungry shark.
Way to take back what's yours, diver!
As this diver demonstrated, carrying a dive knife with you on all underwater adventures is a good idea. Other than helping to untangle yourself, you can fight angry bull sharks to retrieve you speargun. I recommend taking a closer look at UK's Blue Tang knife for your next dive knife.
Available in multiple blade configurations, this rugged underwater blade is aggressive enough to do whatever task you need under the surface.
Better luck next time shark!