Upper body
Surfing: Lying on your board and paddling out against the breakers, paddling to catch a wave, plus "popping up" to standing will develop strong, lean muscles in your back, shoulders, chest and arms. 5 stars
Waterskiing will also build good upper-body strength, as the muscles in your back, shoulders and arms resist the strain of the rope. 4 stars
Lower body
S: Popping up requires explosive leg strength. Once you're up, you'll adopt the half-squat surfing stance and use your legs and body weight to steer the board. 4 stars
W: Tones up your legs fast. They absorb the energy of crossing the bumpy wake behind the boat, control your direction and are bent in a half-squat throughout, giving you particularly strong quads. 5 stars
Fitness
S: Gets your heart rate up, especially in bigger waves, as they're harder to paddle out against. You do get a rest waiting for the right wave, though, so a 10st person would burn about 280 calories an hour. 4 stars
W: A demanding sport that will increase your fitness, but with the strain on your muscles you're unlikely to ski for as long as you can surf. A 10st person would burn about 380 calories if they skied for an hour. 3 stars
Beginners
S: Most people pick up the basics in the white water quickly, but progressing to catching and riding along a wave takes patience. Regular surfing is the only solution - not easy if the sea isn't near you. 4 stars
W: You're likely to progress a little faster in waterskiing. Balance is crucial in both sports, but here you'll learn on still water and practising is easier as you won't be dependent on wave conditions. 5 stars
Avoiding injury
S: Apart from the odd bruise from contact with your board when you fall off, sprains and strains are most common. Working on flexibility and core stability muscles on land helps prevent this. 3 stars
W: A study in the American Journal of Sports Medicine showed that sprains and strains were the most common injuries, especially for advanced skiers as their skis don't come off as easily in a fall. 3 stars
