To setup lake skip, buffer up > upleft > upleft dashes and jump from the water. Do one climbjump on the wall and wallkick on the second jump.
The cue for lake skip is lining up between these two green tiles in the background.

Start an updash here and during the dash and wallbounce, do not hold left, only up.
Make sure to buffer the jump, and only hold left after Madeline wallbounces off the tiny wall.