Finally... I ate my dolphin in the restaurant!
Here's my experience.
1.Before 1:00, try to get as fast as you can, fly at about 1:00.
2.Before 0:30, fly to the space and get higher than Jupiter. (Don't fly too high, the speed would out of control and you may hit the bottom when you go back.)
3.Go back to the water and do a tail-slide then press up to fly.(Watch out for booster and sea bottom, they may kill the dolphin.)
4.Star-slide, star-slide and star-slide.(Sometimes I fly too fast and missed the Neptune star-slide, that makes me lost the chance to reach Pluto.)
The accurate degree may found in Best Comments.
Practice to overcome steps 1 and 2.
Chance is an big effect in step 3 and 4.
Good Luck! and wish you defeat the impossible challenge.
 "Dolphin Olympics 2")