Lake Wakatipu. Queenstown. NZ

Shaped like a perfect cartoon thunderbolt, this gorgeous lake has a 212km shoreline and reaches a depth of 379m (the average depth is over 320m). Five rivers flow into it but only one (the Kawarau) flows out, making it prone to sometimes quite dramatic floods.

If the water looks clean, that's because it is. Scientists have rated it as 99.9% pure – making it the second-purest lake water in the world. In fact, you're better off dipping your glass in the lake than buying bottled water. It's also very cold. That beach by Marine Parade may look tempting on a scorching day, but trust us – you won't want to splash about in water that hovers at around 10°C year-round.