First there surfaced the portmanteau sport of Chessboxing (alternating boxing rounds with ronds of speed chess).
Now there's Swimhiking. Basically, if your hiking route runs you into a lake, you change into trunks, shove your belongings into a waterproof rucksack (a "Swimsac(tm)").
The rucksack and the sport were both invented by Peter Hayes, a university lecturer. The Guardian has run a story about Hayes, and the BBC has two video stories on him and his unorthodox method of navigating the Lake District ("'Swimhiker' takes the plunge" and "River deep mountain high"). So I won't get into repeating what has been said elsewhere.