To find the volume of the lagoon, we need to find the volume of each section and then add them together.
The top rectangle can be seen as a box with a length of 50 feet, width of 20 feet, and height of 0 feet. The volume of this rectangle is 50 x 20 x 0 = 0 cubic feet.
The middle section is shaped like a pyramid with a rectangular base. The base has a length of 50 feet, width of 20 feet, and height of 25 feet. The volume of this pyramid is (1/3) x base area x height = (1/3) x (50 x 20) x 25 = 8,333.33 cubic feet.
The bottom section is again a rectangle with a length of 50 feet, width of 20 feet, and height of 25 feet. The volume of this rectangle is 50 x 20 x 25 = 25,000 cubic feet.
Adding up the volumes of the different sections, we get 0 + 8,333.33 + 25,000 = 33,333.33 cubic feet.
Therefore, the lagoon holds approximately 33,333.33 cubic feet of water.