A concrete pool is formed on site. Builders spray gunite or shotcrete over a steel frame, shape it by hand and finish it in plaster or tile. That makes concrete the choice for custom shapes, infinity edges, built-in spas and commercial pools, and it can be refinished years later.
Fewer companies in British Columbia build in concrete than in vinyl or fiberglass, and several of them have done it for decades. Ask who does the steel and the spraying, what interior finish is included, and how the company handles replastering down the road.