Perhaps surprisingly, Plymouth is the springboard for enjoyable coastal hikes that take in a brace of beaches. The Mount Batten Ferry leaves the Barbican for the Mount Batten peninsula. Walking southeast along the South West Coast Path leads to the compact sandy coves at Jennycliff (1 mile), and then Bovisand (a further 1.5 miles).
From Stonehouse, 2 miles west of the city centre, near the Royal William Yard, the Cremyll Ferry shuttles over to Cornwall's Mount Edgcumbe estate. From there a gorgeous 3-mile hike leads to the fishing villages and sandy beaches at Kingsand and Cawsand. From there, either loop back inland across the Edgcumbe estate, or catch the Cawsand Ferry, run by Plymouth Boat Trips, back to the Barbican.
Plymouth makes open-water swimmers smile. Hardy locals dip in the swim zone beneath the Hoe at Tinside Beach (be wary of currents and conditions). Alongside, the seasonal, historic Tinside Lido is a more sheltered, if equally chilly, dip.