The original water surface of red-violet is set to x feet (the depth of the lake), and when there is no wind, red-violet is perpendicular to the water surface, with a total height of x+0.5 feet.

Because of the wind, I just can't see the red lotus blowing here (submerged in the water, so the fisherman has to go forward to see it). The straight-line distance is 2 feet.

List a triangle (vertical length x, horizontal length 2, hypotenuse length x+0.5), x 2+2 2 = (x+0.5) 2.

X=3.75 feet