Thanks to http://www.heyuguys.co.uk/ and the coolness of Twitter, I found out the following bit of information and have liberally copied it from the boys at HeyUGuys:
On the 4th March, 2009, to mark the UK release of Watchmen, a 70ft water projection screen (the biggest in the world) will be placed between on the River Thames in London between the London Eye and Shell tower building. There will then be a show with Dr. Manhattan coming out of the Thames and rising up into the sky. The production team will then show exclusive footage from the movie onto the water screen. How cool is that?!
IESB.net give more information:
"To celebrate the Paramount Picture UK release of the hugely anticipated and revered Watchmen (in cinemas 06.03.09), at exactly 8pm GMT, London's River Thames will give birth to a Watchmen spectacle that is beyond the thinkable. Dr Manhattan, the blue skinned, super-powered being beloved of all Watchmen fans, will rise above the murky depths of the Thames to a height of over 70 feet and tower over all those who dare to attend.
This dramatic, one-off spectacle will be created using the world's biggest water screen projector. The water screen, moored especially for this occasion in the middle of the Thames between the London Eye and The Shell Building, will create an enormous vertical screen of water that will extend to 72 feet in height and 100 feet across. Specially created, never to be seen again Watchmen footage, will be projected onto the screen to showcase Dr Manhattan's translucent and shimmering form in dramatic and gigantic effect - this really will be an excellent and exciting medium to see Dr Manhattan in all his super human glory; and to watch him hover over the city in true Watchmen style!"