Video: Gulf of Mexico jellyfish swarms

If you’ve ever swum in the Gulf of Mexico, you know … watch out for jellyfish. The swarms can be massive under the best of conditions, but if the ecosystem is nudged toward the unhealthy side, look out. The swarms of jellyfish become colossal. In this way, scientists say, jellyfish in the Gulf of Mexico are like a canary in the coal mine, warning of possibly dangerous environmental changes in the water.