The DIY presentation is perfect for one-off constructions or repairs or alterations and home owners who do not want to invest in the contractor presentation and applicator gun. The DIY presentation is our best selling product. Black Waterfall Foam is a low expansion, high-density foam used in the construction of natural looking waterfalls and streams. It is fish safe and non leaching. The Foam expands to fill voids between the rocks and liner, diverting water over the top of the stones. It cuts down the time required to build waterfalls and streams thanks to its quick curing time and ease of use. Waterfall Construction Foam has fundamentally changed the water feature construction industry because it simplifies waterfall construction and is easier to use than mortar.