Marine isopods show up in the news from time to time. These are basically giant, sea-going cousins of the roly-polies and pillbugs that hang around homes here in Kentucky. Fox news issued a report about one recently: this one was over 2 feet long. The ones I have read about before are only about 1 foot long. Neat critters. They supposedly scavenge whale and squid carcasses on the ocean floor. By the way: isopods are not insects, they are crustaceans. This means that they are more closely related to lobsters and crabs than beetles and butterflies. And I am convinced that a giant isopod would taste great with drawn butter and a little salt.
Here is a wikipedia entry with lots of info about giant isopods.