When many people think of swimming, they think of pools and lanes, but wild swimming and open water swimming have become extremely popular in recent years. Open water swimming marathons are increasingly popular and they are included in events such as triathlons.

The Norseman Xtreme Triathlon is considered to have one of the hardest open water swimming tasks. Swimmers are dropped from a ferry 12 feet into the icy waters of the fjord. This event starts with the swimming so when this section is finished they just get on with the cycling and the running.

For slightly warmer waters, you could head for the Waikiki Roughwater Swim. This swim used to be part of the Ironman World Championship but it is challenging for any swimmer as it means dealing with very rough waters and strong currents.

The Manhattan Island Marathon Swim is an event that dates back to the 1920s. Only 25 swimmers are permitted to take part on this course which covers around 28.5 miles around the island. The water temperatures are fairly cold and swimmers have to deal with boat traffic, floating debris and rough waters. There is also quite a steep entry fee.

For a really challenging swim, what about one that has only ever been completed by two people? The marathon swim from the Farallon Islands to the Golden Gate Bridge means that you might have to face an obstacle or two, including a great white shark. Participants are not allowed to wear wetsuits.

In South Africa you could try the Robben Island to Three Anchor Bay swim. At 6.3 miles it is not the marathon distance you might be looking for but it is not for the faint-hearted due to the challenging conditions such as the choppy seas and wind.

One of the most iconic open water swims is the English Channel, where many swimmers have attempted to cross the shortest stretch between England and France, which covers 20.7 miles. The first swim took almost 22 hours but these days you cannot simply head to the water and start swimming as it has to be regulated. This is a very busy stretch of water, so you have to plan well in advance. Some people spend a few years on a waiting list and have to have the funds to run a support boat, as well as providing evidence of previous long distance swims.

For Scottish lake swimming consider the Loch Ness open water swim. This covers 23 miles and it is a very difficult swim. The water is cold and occasionally visibility is extremely low. Those who just want to get a taste of the event can take part in the monster swim, which covers just one mile.