IRONMAN 70.3 Oceanside is a triathlon event located in Oceanside, California. The course begins with a 1.2-mile swim in the calm waters of Oceanside Harbor. Athletes start the swim on the beach and swim out to the harbor, where they will complete a rectangular course before returning to shore. The swim is known for its clear, blue water and the stunning views of the harbor and surrounding coastline. After completing the swim, athletes transition to the 56-mile bike course, which takes them ...