 The opening and closing times of these windows varies from race to race with the longer races have earlier start windows and/or later finishing windows.Races C and D include Savernake Tunnel, where overtaking is prohibited due to safety reasons.The Waterside Series attracts a range of entrants from regular marathon paddlers based at clubs around the country to endurance athletes from other sports seeking to use the races for training, the race is also popular with public schools and the military.