HBO Sports' latest documentary "Momentum Generation" focuses on surfing stars who redefined the sport in the 1990s, but the larger story is about how the surfers evolved from extended adolescence to middle age.

With the two-pronged approach of extensive interviews and archival digs, directors Michael and Jeff Zimbalist were able to bring texture and context to the personalities and their relationships. As friends and rivals -- and both -- these surfers seemed to relish the opportunity to put their contributions into historical perspective.

"Momentum Generation" premieres December 11 at 10 p.m. ET/PT on HBO. It is already a critical hit with awards from film festivals including Tribeca, Aspen, Santa Cruz Surf, Honolulu Surf and Surfalorus. Check out the video above for some insight from the directors and surfers Rob Machado, Taylor Knox, Pat O'Connell and Taylor Steele.