What widespread submarine snorkels would change in World War II

How would the Second World War change if every major navy used submarine snorkels widely?

Snorkels could save some boats forced to operate submerged, but adding them to existing designs would complicate exhaust, machinery, conning-tower arrangements, and construction schedules.

Dutch experience gave Britain access to the snorkel concept, and the Royal Navy considered it for boats operating in the Mediterranean. Allied long-range cruising submarines were not initially optimized for prolonged submerged running, so the benefit was smaller than it would later become for boats forced below the surface. A reliable installation required more than adding a tube: exhaust routing, engines, internal plumbing, and the conning tower all needed integration. Retrofitting those systems could delay construction and introduce new faults. The panel therefore expects wider snorkel use to save some submarines while making the strongest case for designs built around it from the keel up.