How many times have we had the 'round Portsmouth' conversation at the church
Hightower, Iím glad you noticed the water level under that bridge, as itís the one I always mention.
As you say, at high tide you could possibly just about swim under it.
At Low tide you would have to walk it.
As Pete says, when there is enough water for a RIB, any sort of A-Frame etc wouldnít go under.
In my opinion itís a SIB only job, at mid tide, and youíd need to do the bridge under the Eastern road at the same time.
The channel under the M275 is almost dry at low water, but is plenty high enough at high tide to take a RIB with the biggest of A Frames.