South Devon pairs Plymouth's serious boat-diving infrastructure with Torbay's flexible shore entries. The headline days are wrecks such as HMS Scylla and James Egan Layne, reef scenery at Hand Deeps, and shallow wildlife searches from Brixham Breakwater Beach. Water is temperate, visibility is variable, and weather can rewrite a charter plan, so local skippers, redundant surface-signalling equipment, and realistic cold-water skills matter more than a rigid wish list. May to September gives the broadest overlap of warmer water, longer days, guided snorkeling at Wembury Bay, and more reliable boat schedules. Experienced local divers continue through winter when forecasts cooperate. The destination also works unusually well for mixed groups: Plymouth adds the National Marine Aquarium, the Barbican, and coastal history, while Torbay adds the English Riviera UNESCO Global Geopark, beaches, and the South West Coast Path.