(CNN) Environmentalists warn that a large "ghost net" is floating in Hawaiian waters that could threaten marine life and cause severe damage to boats if not removed soon.

Ghost nets are massive fishing nets that have been left or lost at sea by fisherman.

Officials are asking people to be on the lookout for what they believe to be a net measuring 50 feet long by 70 feet wide, and approximately 50 feet deep in the sea, according to Matt Lane, a spokesman with the nonprofit Love the Sea.

Mary Crowley, founder of Ocean Voyages Institute, which conducts ocean debris cleanups, told CNN it's difficult to know the exact size since there have been sightings from different people, but no photos.

She said when people spotting nets take photos of them, rescuers can get a more accurate estimate on sizing, which helps determine extraction efforts.

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