In 1992, big wave surfers such as Laird Hamilton and Darrick Doerner introduced a cross over sport called tow in surfing. While many riders still participate in both sports, they remain very distinct activities. This type of surfing involves being towed in to massive waves by jet ski, allowing for the speed needed to successfully ride. Tow in surfing also revolutionized board size, allowing surfers to trade in their unwieldy 12 ft. boards in favor of light, 7 ft boards that allowed for more speed and easier maneuverability in waves over 30 ft. By the end of the 1990s, tow in surfing allowed surfers to ride waves exceeding 50 ft.
Source: Wikipedia, Stonesreef Surfshop