how do you get tidal wave

It is in the fourth geyser, and all of the walkthrough's that I have read have completely missed or neglected to mention it.

As you near the completion of the geyser there is a part where you are once again forced to jump into the water in order to reach a certain destination. While you are in the water press down and left and you will find yourself next to a lone island with a treasure chest. That's tidal wave.

Unfortunately I do realize that there are several sequences where the quick water is abundant, but I cannot remember which part has tidal wave. Just try all of the different drop offs and you will eventually find it.