While they haven't achieved the film celebrity of sharks, jellyfish — colorless, tentacled creatures — are far more likely than sharks to hurt humans, says John McCord, manager of education at the Aquarium of the Pacific in Long Beach, Calif.
More correctly called "sea jellies" these creatures range from a couple of inches to three feet across and have long, spindly tentacles that pack a sometimes painful sting.
Typical stings are pretty mild, bringing on a burning sensation and rash that can go away within a few minutes. Get out of the water, recommends McCord, if you feel a bee-like sting — calmly and slowly, though, to avoid getting stung again by the same critter.
Go to a lifeguard, who might rinse the area with salt water and apply vinegar to neutralize the venom.
Some types of jellies, such as sea wasps found in Australia and Portuguese man-o'-wars found on the East Coast of the United States and in other parts of the world, can emit a toxic venom that can be serious, or in rare cases — fatal.
The stingray is also a venomous creature. Its sting, which usually is provoked by stepping on its back, can be very painful for up to two days. Seek medical attention from a lifeguard or a doctor; something as simple as applying very hot water to the painful area can give some relief.
Better yet, avoid getting stung in the first place: shuffle your feet as you wade into a sandy-bottomed area. That keeps you from stepping on the stingray's back and gives the animal a chance to swim away.
The so-called "stingray shuffle" works, McCord explains, because the rays "don't want to sting you any more than you want to be stung."