Which of the following is NOT a type of pool or spa surfacing?

The correct answer identifies a type of surfacing that is commonly used in pools and spas. Cement is indeed a type of pool surface, often used in the construction of gunite or shotcrete pools, where a mixture of sand, gravel, and cement is applied to create a sturdy and durable shell. Various finishing techniques can be applied over this cement structure to improve aesthetics or texture.

The other options listed—paint, tile, and fiberglassing—are all legitimate methods or materials used to surface a pool or spa. Paint is often used for a more economical finish but requires regular maintenance and may wear out faster than other methods. Tile provides a more luxurious appearance and is highly customizable but can be more expensive and requires skilled installation. Fiberglassing is a method for creating a smooth, non-porous finish that is very durable and resistant to algae growth. Thus, cement stands out as a foundational construction material rather than a surfacing option in the context of pool and spa finishes.