The key to this achievement is...cutlery
1) place the controller on the table/ a surface in front of you
2) Get a teaspoon
3) place the curved side of the spoon between the A and B button
4) get a perfect start (as in: jump in the water on the word GO!)
5) insanely move the spoon up and down, alternately hitting A and B
It'll be much easier to maintain full speed than the thumbstick method and you'll be able to clear the time.
Good luck!