This should come in normal story progression. There are several jet streams throughout the game and dozens of schools of fish. When you pass through a school of fish, a light flashes and there is also an audio cue. This tells you that you have 'burst' a school of fish. When you burst the 15th school, the achievement unlocks.
The game keeps track of the schools of fish you burst even when you quit the game in mid-chapter. So, if you don't want to wait for the achievement to come naturally, the earliest opportunity is right at the very beginning of chapter 2.
As part of normal game play, you begin chapter 2 by turning right and entering a jet stream. After you have burst 8 or 9 schools of fish, press
and select
Main Menu. From the main menu select Continue. You will find yourself at the beginning of chapter 2. Turn right and enter the jet stream again. Your burst schools of fish count continues from where you left off before quitting the game. So, if you had 8 burst schools of fish earlier, the achievement will unlock once you add 7 more burst schools of fish to the count.
If it takes you a short while to get accustomed to the controls, you can quit to the main menu and continue the game as many times as you need to get the achievement. There is a big advantage to getting the achievement out of the way early. For example, in the next jet stream you encounter is a misssable Sea Shell. Your concentration will be much improved if you don't have to worry about bursting schools of fish.