How can a sea urchin kill you?

Answer 1

Lots of awesome things! Each spine fits into a rotator socket, allowing the urchin to move all spines independently. This allows them to catch food and move it towards their mouths, walk around, burrow into shale, and cover themselves in kelp and other material for camouflage.

Answer 2

Sea urchin venom is typically delivered via claw-like structures called pedicellaria. The spines may or may not be venomous, as well. Puncture wounds from the spines can be a site of venom injection, infection, and tissue damage. The venom itself can cause fatigue, muscle weakness, paralysis, respiratory distress and eventual death.

If the victim stays in the water, muscle weakness and fatigue can easily lead to drowning, as well.