The invention relates to a novel water open caisson construction technology. An open caisson is prefabricated in a land precast yard in one step, and a cutting edge angle is arranged on the bottom of the open caisson; a compressed air pipe is vertically arranged along the inner wall of the open caisson after prefabrication; high-pressure air nozzles are mounted on the pipe end; the upper part of the vertical compressed air pipe is connected by a compressed air parallel pipe; the open caisson is conveyed to a construction position, is hoisted by a floating crane or is positioned by a buoyancy tank; an air compressor is connected with the compressed air parallel pipe; the air compressor is started to convey compressed air to the compressed air pipe, and the open caisson slowly sinks; compressed air is ejected from the high-pressure air nozzles at the bottom; a soil body is cut by virtue of explosive force of the compressed air; and after being discharged, the compressed air rapidly moves towards the water surface in water, and cut soil upwards moves along with the compressed air, so that the inner wall of the open caisson and the soil body are isolated, and the open caisson sinks under the effect of self weight. The invention is applicable to a foundation with a uniform soil property, and is particularly applicable to a sludge or sandy foundation; the construction speed of the water open caisson can be greatly quickened; correction and leveling are facilitated; the apparatus is simple; the technology is simple and convenient; and the construction cost is reduced.