Sean Collins, the founder of Huntington Beach-based Surfline, has died, according to the company. Surfline is the go-to site for surfing forecoasts, and was based on Collins' development of surf forecoasting methods over the last 30 years. The company said Collins died of a heart attack while playing tennis Monday. Surfline had originally started as phone-in surf forecast service in 1985, which Collins later transformed into one of the largest sports websites in the world. Collins was 59.