Half Distance Triathlon Weymouth, Dorset, England: Ultimate Race Guide. SWIM - Start your triathlon journey with a 1.2-mile (1.9 km) swim in Weymouth Bay. The single-loop triangular course offers a scenic and smooth swim, beginning with a straight stretch away from Weymouth Beach, followed by two right turns guiding you back to transition. Average Water Temperature: 63°F (17°C), ideal for wetsuit use. BIKE - Experience a picturesque 56-mile (90 km) bike route through Dorset’s rolling ...