A seal in Hawaii had a few people worried as it played with a knife as if it was a toy.

The seal can be seen in a video swimming in a pool off a beach on Big Island while holding an orange fishing knife.

It drops it, picks it up and drops it again in the water.

The seal can be seen swimming in a pool off a beach on Big Island while holding an orange fishing knife. (Supplied)

The monk seal pup named Manu’iwa was lucky it didn’t swallow the blade.

Staff members from Ke Kai Ola, who run the Marine Mammal Center at Kailua-Kona, were able to retrieve the knife once the pup dropped it under rocks in the water.

Manu’iwa is an endangered species. (Supplied)

“There was real concern that the seal pup might swallow the knife,” the DLNR Division of Conservation and Resources Enforcement officer who recorded the video on Sunday said.

“It’s a reminder to all of us to properly dispose of our trash and not to leave it in Hawaii beaches or in the ocean.”

Marine experts are now urging people to throw away rubbish and be mindful where weapons are placed to ensure endangered marine life will not be threatened or injured.

Marine experts are urging people to throw away rubbish. (Supplied)