I think you found a diamond!

On an afternoon while on vacation in the Indian ocean , you walk to the end of a dock and, shine your amazing red light point into the water. When you shine the beam of light on the water a horizontal distance of 2.4 m from the dock, you see a glint of light from a shiny object on the sandy bottom–(a diamond ). If the your red pointer is 1.8 m above the surface of the water, and the water is 5.5 m deep, what is the horizontal distance from the end of the dock to the shiny object?