What materials stop water from flowing the best?

The materials that stop water from flowing the best are typically those that are impermeable, meaning that they do not allow water to pass through them. Some examples of such materials include:

- Metals: Metals such as copper, aluminium, steel, and iron are impermeable to water and can effectively stop water flow.

- Glass: Glass is another impermeable material that can prevent water from flowing.

- Plastics: Certain types of plastics, such as polyethylene, polypropylene, and PVC, are also impermeable to water and can be used to stop water flow.

- Rubber: Rubber is a flexible material that is often used to make gaskets and seals to prevent water leakage.

- Concrete: Concrete is a mixture of cement, sand, and gravel that is often used in construction. It is impermeable to water and can be used to make dams, reservoirs, and other water-retaining structures.

- Asphalt: Asphalt is a black, sticky substance that is used in paving roads and parking lots. It is impermeable to water and can be used to prevent water from seeping into the ground.