A Devon man with two decades of service in the Royal Marines is approaching the final stretch of an extraordinary oceanic feat that has already consumed more than 300 days of his life. Dave "Dinger" Bell, 54, departed from Lima in Peru on November 9 last year and now finds himself 900 nautical miles from the Kenyan port of Mombasa, where he expects to arrive in early October.Should he succeed, Mr Bell will become the first individual to complete…