How to Identify Jellyfish

Many are fascinated with the mysterious, beautiful and slightly dangerous nature of jellyfish. Unfortunately, jellyfish have a tainted reputation and are feared by many because of their power to sting. It's a good idea to take proper safety precautions when swimming, and the first step toward safety is the ability to identify this creature. Here's a quick guide to recognizing jellyfish.

Instructions

1. Have an eagle eye. All species are difficult to see because of their transparent bodies and the fact that they are about 98 percent water. Look for clear, jelly-like, free-flowing bodies that appear as if your hand would go right through if you tried to touch them.

2. Check the shape. Nearly all kinds of jellyfish have a rounded "hood" that looks like a mini-dome tent or the top of a mushroom. The length, width and thickness of these hoods will vary.

3. Recognize symmetry. Most species of jellyfish are evenly built. In other words, if you cut a jellyfish in half, you would have two equal parts.

4. Look for tentacles. Most types of jellyfish have tentacles that help them catch food and sting prey (and people). Long, clear, floating string-like legs stemming from a round dome-like head is a good indicator that you have found a jellyfish.

5. Spot jellyfish with color. Although we think of jellyfish as being primarily clear, some species have browns, pinks, oranges and blues inside the transparent hood of their upper body. For example, the blue jellyfish, which is quite common and can sting, can vary in color from a deep blue to a chalky white. Colored jellyfish will still have the symmetrical shape and hooded body.

6. Study the movement. Jellyfish are smooth, even and agile swimmers. They will never make choppy strokes. You can rule out any fish that make rigid strokes--they are not jellyfish.

Tips & Warnings

• There are approximately 200 species of jellyfish, most of which live in saltwater only. If you are planning a trip to a tropical location, study pictures of the many types of jellyfish, and you will feel better prepared to avoid the stinging varieties. Don't worry--there are not nearly as many stinging types as people think.

• The two most dangerous species of jellyfish are the box jelly and the Irukandji jellyfish. Both of these species can kill someone with their sting. The box jellyfish is large and usually has many tentacles (up to 60). It has a box- or bell-like shape and can swim very fast. The Irukandji jellyfish is tiny, less than an inch wide. Both are found only in tropical waters.

• Beware of jellyfish that have been washed up on a beach. While the most dangerous species are fast swimmers and rarely wash up, other smaller forms of jellyfish can easily be pushed onto a beach. Watch your step on a tropical beach.