The Ice Mile is described by The Guardian newspaper as 'the toughest swimming test on the planet' and few who have been brave enough to take on the challenge would doubt this. https://www.theguardian.com/lifeandstyle/the-swimming-blog/2014/jan/07/ice-mile-swimming-test-planet
The Ice Mile is a personal challenge for an experienced Ice Swimmer and involves swimming one mile ( 1609 metres ) in water temperature of 5 degrees or less with just a swimming costume, one normal silicone swimming hat and goggles ( nose clips and ear plugs are also allowed ).
For most swimmers this will mean being in the water for between 25 and 45 minutes in an extreme enviroment where hypothermia is a real risk. For the swimmer's safety IISA insists on an observed qualifying swim being successfully completed before an Ice Mile is attempted and also the swimmer must undertake a medical examination including ECG.
To be approved as an official IISA Ice Mile the swimmer needs to provide documented evidence of the swim including specified video and photographic evidence and the swim must be observed by two IISA members. When an Ice Mile has been approved by IISA it appears in a log on the swimmer's bio information page on the IISA website.
Full details of the requirements for an Ice Mile can be found on the IISA website http://www.internationaliceswimming.com/iisa-rules/