The boat chase was not originally intended to be part of the opening sequence but test audiences indicated that the jump out of the window opener was not exciting enough. As such, the boat chase was brought forward and had to be shortened. As it is now, the Bilbao - Mi6 HQ - Boat Chase opener is still the longest pre-credits sequence ever in a James Bond movie.
In the scene where Bond is traveling through the waterways of London on his speedboat, he soaks two officers in the process of clamping a car. They're the two stars of the BBC show "The Clampers". They did not know what they were there for and were just told to clamp the car.