How do engineers build long bridges in water?

Watch this documentary , it gives a clear idea about how long bridges are built in water. In short precast technology is the trend for constructing bridges in water. From foundations to decks everything can be precasted off-shore and then placed in position. Segments are carried on barges and lifted using cranes. read more

There are many ways to build bridges over water, depending on specific site conditions, technology prevalent in the country and technical capability of the contractor. All bridges (except floating ones, which are rarely used permanently), need a foundation, which is rested on the bed. read more

No need for cofferdams. Just get a long enough pile and drive it into the bed of the river, much like the wooden docks and piers of today. 2. "Concrete" bridges, or more appropriately, masonry bridges built of giant stones/rocks/bricks. Get a bunch of slaves to put the brick where you want it and keep building up until you get out of the water. read more