Sea Turtles would hunt and eat the smaller jellyfish, but not the giant jellyfish.
No.
There are giant jellyfish found throughout the ocean. Depending on the breed, the pattern of migration is pattern. For example a Nomura jellyfish is often found around Japan.
Cyanea Capillata (lion's mane jellyfish) is said to be the world's laregest jellyfish.
Cyanea capillata
Pikes, sharks, giant squids, giant octopus, sea birds, jellyfish, and people.
Ghasts are one of the biggest mobs in minecraft. They look like giant jellyfish.
Not of the kind in myths and fantasy. Giant squids, jellyfish and whales etc do exist.
They probably want fish and dead whales caught from the Japanese fishermen to eat.
The lion's mane jellyfish (Cyanea capillata) holds the title for being one of the largest jellyfish species. They can have bell diameters reaching up to 8 feet (2.4 meters) and tentacles that extend as long as 100 feet (30 meters).
The largest jellyfish ever recorded was an Arctic Giant that was washed up in Massachusetts Bay, USA in 1870 which had a bell diameter of 2.28m (7 ft 6 in) and tentacles stretching 36.5 m (120 ft).
Moon Jellyfish is the most common. Some of the more poisonous types include the Portuguese Man O' War, the Box Jellyfish, and the Irukandji. There's a type of giant jellyfish in Japan that I don't remember the name of, but it would probably be easy to find.