NANTUCKET (CBS) – A 25-foot whale is swimming extremely close to passing boats and ferries in Nantucket Harbor.

At one point, boat traffic had to be briefly blocked and boaters are now being told to go slow.

The whale has been seen just 100 feet off shore, giving crowds a thrill.

Officials say it is a minke whale, which usually travels alone or in small groups. The species is not endangered.