Very big ships that carry a lot of oil or other liquids.
Supertankers are important for moving a lot of oil from one place to another, but they can also cause big problems if they spill their oil.
Examples:
The supertanker sailed across the ocean.
Supertankers can carry millions of gallons of oil.
The supertanker is too big to fit in the harbor.
The supertanker is like a giant bathtub for oil.
The supertanker is longer than a whole street.
The supertanker is so big, it looks like a floating city.