Swindon army dog handler Corporal Nobby Clarke joined seven-year-old Lenny to take part in the Army Dog Unit Canine Biathlon in Ballykelly.
Nobby, who is currently on a two-year operation tour of Northern Ireland, led Lenny through a test of stamina and endurance over a four-and-a-half-mile cross-country course.
Competitors encountered a variety of obstacles, including ditch crossings, wading through freezing water hurdles, jumping over equestrian jumps and ducking under bridges.
The handlers had to carry their dogs for a section of the course and also fire shots on a 30-metre range.
Nobby said: "It was extremely tiring, very wet but good fun.
"Lenny was in his element in all that water."
The aim of the competition was to bring dogs and their handlers from all over he province together to test their physical fitness, skills and have some fun in the process.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article