Glenn Druery entered his Tonkinese cat, Gus, as a wild-card contender in the Scotland Island dog swimming race, which has been held every Christmas Eve for the past 44 years. Although Gus is unlikely to win the race because of the physical advantages dogs have over cats, it does make for a good story.
Other dog owners who joined the race weren’t too hot about the cat joining the race in the interest of the safety of Gus and the other dogs too. In general, “[b]ig water dogs, such as labradors and other retrievers, predictably fare best overall.” The winners are categorized based on 3 dog sizes and receive their respective share of the prizes, which doubles as the entry fee of a beer bottle and a tin of dog food.
The Guardian gives more details about the origin of this holiday tradition here.