September 22-23, 2018. Half Marathon, Half Marathon Relay, 5k, Triathlon, Duathlon, Aquabike & Tri & Du Team Relays. Run, Bike & Swim Bethany Beach's beautiful and clean air and ocean waters. Bike along one of the most tranquil and scenic areas of Coastal Delaware and run through area towns along the coastline. You will no doubt discover why Bethany Beach was just named as one of the "best secret beaches on earth" by Travel & Leisure.