Record keepers say the lion's mane jellyfish they come across in Maine are usually are about a foot and a half to 2 feet in diameter, but there have been a few reports of ones that are 5 to 6 feet.
The tentacles can sting and are used to grab its prey. If a human is stung it will be painful but not usually life-threatening.
Nick Record, a senior research scientist at Bigelow Laboratory for Ocean Sciences, said "Just a gigantic, scary jellyfish that you would not want to run into in the water. It has been kind of a steady stream of them all summer," according to the AP.
So far the number of sightings is not unusual, Record said, with the number expected to be between the normal 300 to 700 jellyfish they typically see.
But experts say that while the number isn't unusual, the size of the ones being found may signal a climate change.
Record said that the Gulf of Maine is getting warmer than other bodies of water and the jellyfish will get bigger in warmer water, according to the AP.