Crew and passengers aboard a Maui Dive Shop boat say they saw a large shark bump up against a kayak about a mile off Makena's Big Beach Wednesday afternoon.

Servin, his wife, Martie, and about two dozen other people were aboard the snorkel cruise when they saw what they thought was a small whale. Servin said he saw the shark hit the back of a kayak, which was being operated by a middle-aged man.

Boat Capt. Rae Stewart said she could see the shark at the back of the kayak when they approached, and she got close to the shark in an effort to spook it away from the kayaker. It eventually swam away.

Later the kayaker and a companion on another kayak were taken in to shore at Makena aboard the Maui Dive Shop boat, with their kayaks in tow. The two men reportedly are visitors to Maui; Stewart did not have their names.

Beaches remained open, but enforcement officers were at beaches from Wailea to La Perouse warning beachgoers about the sighting. State and Maui County aquatics specialists also notified hotels, the Coast Guard, fire, police and boaters of the sighting and the shark's reported behavior.

As of Wednesday afternoon, the shark had not been spotted from the shoreline. A Maui County ocean safety official said lifeguards were not called out to patrol the waters.

The kayaker told someone that the shark had been following him for about 15 minutes, sometimes nudging his kayak. The shark was estimated to be 15 to 18 feet.