© International Olympic Committee (IOC)
1908 Diving venue: White City Stadium
An entirely novel feature is the swimming bath, a rectangle of 100 metres by 50 feet, with a depth at each end of 4 feet 6 inches, and a middle depth of 12 feet 6 inches. There is a collapsible tower of the regulation height to allow of high-diving competitions. The arena is surrounded by a stand with accommodation for 70,000 spectators, and provides dressing rooms, lavatories, etc., for the competitors in the games.
One of the chief elements in the success of the swimming events at the Olympic Games of London was the fact that the swimming bath in which they took place was, for the first time in the history of these Games, constructed in the same arena which was used for the other important international competitions. For the plan of construction of this bath, and more especially for the original design of the tower for high diving, the hearty thanks of the British Olympic Council and of all international swimmers are due to Mr. William Henry, Chief Secretary of the Royal Life Saving Society. The tower was let down beneath the surface of the water when not required for diving and raised again in a few minutes according to the necessities of the programme.
Source: 1908 Summer Olympics official report (read)