Sean Collins, 59, who created Surfline.com, whose forecasts and real-time views of beaches reach 1.5 million surfers a week, died Monday in Newport Beach, Calif.

He had a heart attack while playing tennis, his business partner, David Gilovich, said.

Before Surfline, dedicated surfers would hang out on the beach for weeks at a time, dropping everything, including work and relationships, when the surf came up. Mr. Collins' forecasts meant that surfers could use their time more efficiently. It allowed them to continue to chase swells through what he termed "the responsible years" and gave rise to a breed of plugged-in surfers who make their living through high-dollar contests or by chasing monster swells.

"Sean was a renaissance man," said Bill Sharp, director of the annual Billabong XXL Big Wave Awards and a longtime colleague. "He could see something that was needed long before anyone else."

Mr. Collins' forecasting prowess was self-taught. He scrupulously logged daily surf conditions, studied obscure National Weather Service archives, and used a shortwave fax machine - stringing antenna wire across Baja cactus plants - to receive weather reports from New Zealand and understand how Antarctic storms could send waves across the Pacific. His predictions astonished friends.

He joined a telephone forecast venture called Surfline in 1984, and two years later began a rival service called Wavetrak. He bought out Surfline in 1990 and five years later started Surfline.com.

Forecasts were refined with the help of Jon Chrostowski, a NASA scientist who hacked into data streams broadcast by weather buoys, and William C. O'Reilly, an oceanographer with the Scripps Institute who modeled the interaction of waves with the seafloor.

Mr. Collins was born in Pasadena, Calif. He sailed the coasts of California and Baja, Mexico, with his father, a Navy lieutenant, and developed into a talented competitive surfer. He explored the Mexican outback extensively. - N.Y. Times News Service