How a bridge on the sea or a river is build still having a lot of water?if web page aviable please send me?

Bridge piers are placed within waterways using a number of techniques. In some circumstances the stream can be diverted enabling work to proceed in the dry. Probably the most common method is use of the cofferdam.

Definition of cofferdam: http://www.bartleby.com/65/co/cofferda.html

Pictures of cofferdams:
http://www.wai.com/Construction/cons-coffer.html

http://www.lrl.usace.army.mil/olmsted/cd_pics/950808bb.htm

http://www.ororkebridge.com/images/sept01/full/Pier-2-Cofferdam5.jpg

Picture of an ancient Roman cofferdam:
http://www.glendale-h.schools.nsw.edu.au/faculty_pages/ind_arts_web/bridgeweb/romancoffer.html

The Bridge construction in Sea or water is carriedout by using Precast segments from one end (at ground) by constructing piles. Many machineries are used during such type of construction like barge. Barge is nothing but a working platform which is shifted from one place to other place by duck boats through sea route. It equipped with all required machineries like concreting Plant, Piling hammer etc. After shifting it to other place it is anchored through anchors in the sea. Ultimately this provides a working platfrom for the team during construction. For shifting of materials like precast materials also some time we use barges.