Corals

Their Weapons:

Shame on you. Brushing against coral removes its protective mucous
coating. Although the nematocysts of coral polyps can't do much damage to
humans, they have other ways of paying you back: cuts and abrasions from
the sharp points and razor edges of stony corals.

Effects:

Burning pain and itchy welts. This "reef rash" (a form of coral poisoning) can
take up to six weeks to heal completely.

Rx:

Scrub area with soap and water. Rinse stinging wounds with 5
percent vinegar solution or isopropyl alcohol.

Apply hydrocortisone ointment.