After a seven-month process, the 160-meter (525-foot) long sweeping roof frame was put into place Wednesday. The structure weighs more than 3,000 tons and rests on three concrete supports.
Organizers described the project as "one of the most complex engineering and construction challenges" of the Olympic building phase.
Work will begin soon on the aluminum roof covering.
The wavy roof - designed by Iraqi-born architect Zaha Hadid - is considered the signature design feature of the Olympic Park in Stratford, east London.
The 300 million pound ($500 million; ?335 million) aquatics venue is scheduled to be completed in the summer of 2011. Organizers say it will be the "gateway" into the park complex for spectators arriving by public transport.
The 17,500-seat venue will host swimming, diving and the water polo finals during the Olympics. It will be reduced after the games to a 2,500-seat facility.
