At an ocean depth of 20 meters, a buoy bobs up and then down 2 meters from the oceans depth. Four seconds pass from the time the buoy is at it's highest point to when it is at lowest point. Assume at x=0, buoy is at normal ocean depth Use the sine tool to graph the function. The first pint must be in the midline and the second must be a maximum or minimum value on the graph closest to the first point

We'll use a sin graph since at x=0 the buoy is at the y midline

the period is 8 seconds  (highest point to lowest point and back to highest point)

Frequency is   1/period     1/8

Starts at 20  (sine wave shifted up 20 m)

Amplitude  2   (up 2 meters then down 2 meters below norma ocean depth)    ( I think this is what you meant in your questionif it bobs UP 2m then back to normal depth then down 2m)

2sin((2pi x)/8)   + 20

Step-by-step explanation: