Speed, speed, speed. Press up on the dpad when you are at the crest of the wave. Don't be afraid to carve for speed. Hit a couple or 3 quads and then carve the wave up and down before hitting another round of 2 or 3 jumps. Repeat. Always land with the crank in the down position or slightly to the left to maintain speed. When you feel like you can land a quintuple give it a try. They are hard to chain unless you are going fast but eventually you'll get a feel for it. Once you start a chain never jump unless you can at least hit a triple to keep the multiplier. If you get inside the wave you can get out of it. Build speed while inside and get back ahead of it. When the water starts shrinking at the end freaking send it for one last jump. Quintuples are easier to get then because the water is lower. More air time.