General view of the Swimming Stadium and the spectator’s tribune in Stockholm 1912 Olympic Games. The Stadium, venue of Swimming, Water Polo and Diving competitions, was a temporary construction, fixed on the waters of Djurgårdsbrunnsviken, which offered the greatest advantages, as regards natural facilities for the building of stands along the shores. In addition, the waters offered a protection against currents. To note that none of the open air swimming baths of Stockholm could be used for the purpose, the largest not measuring more than 33,3 metres in length, while the International Rules for Swimming Competitions prescribe a minimum length of 100 metres for swimming races above 500 metres.
Source: Den Femte Olympiaden i Bild och Ord. – Official report Stockholm 1912 Olympic Games