Obviously the lido never did appear, which is a real shame: it would have been an Olympic-size pool, 40 metres out into the river, which rose and fell with the tide. A clear covering was to offer swimmers all-round London views, and could close to protect them from bad weather. See the architects' image here.
So what went wrong? Unfortunately, it proved just too expensive - and so disappeared like so many British lidos. Instead, the current plan is for an ordinary indoor pool - as part of a controversial high-rise development.