They’re also dangerous to humans:
The bright colours and patterns of cone snails have led curious or inquisitive people to pick them up, sometimes with tragic consequences when the snail fires its harpoon in self-defense. About 30 human deaths have been recorded from cone snail envenomation. One species, Conus geographus, is known colloquially as the “cigarette snail,” in the belief that the victim will have only enough time to smoke a cigarette before perishing. The harpoon can penetrate gloves or even wetsuits. Symptoms of a cone snail sting include intense pain, swelling, numbness and tingling. Symptoms can start immediately or can be delayed in onset for days. Severe cases involved muscle paralysis, changes in vision and respiratory failure that can lead to death. There is no antivenin, and treatment involves providing life support until the venom is metabolised by the victim.