The focus of this study is upper Gulf off the mouth of the Chao Phraya River of Samut-prakarn province in Thailand. Chaopraya river is characterized by a large potential for material recycling and maintenance. This river is connected to a maze of mangrove-lined narrow channels and dismisses into ocean inlet. One of source of pollution is fossil oil effluent from the general cargo ship because of the major port city. Therefore, some of fuel oil might be contaminated to the river and also flow into gulf of Thailand mostly concentrated around estuary area. Another source of pollution is the urban seawage from the city located adjacent to shores of river, and discharge from a number of small cities along it.