That's it, we're adding Japan to the list of places where we are never going swimming -- right after Australia (crocodiles and sharks) and Loch Ness (can't be too sure 'bout Nessie).

Not only do you have to keep an eye out for sumo wrestlers in Speedos, there are also swarms of sumo-wrestler-size jellyfish to contend with.

These monsters, which can grow to over 7 feet in diameter and weigh over 660 lbs., are said to be appearing in plague-like proportions off Japan's Pacific coast, where they are threatening to ruin the local fishing industry.

Because of their mass, the giant Echizen jellyfish are wrecking fishermen's nets and crushing catches. And that's if they can even be reeled in; one of these monsters recently capsized a fishing boat after getting caught in its nets.

Experts think global warming could be to blame for the swarms, which have drifted from their spawning grounds in Chinese and Korean waters. They also say over-fishing has depleted the number of fish which would prey on the jellyfish before they grow to monumental proportions. The jellyfish invasion is already said to have cost the Japanese fishing industry millions of yen. Keep reading to see a vid of the jumbo jellies.