Marine underwater assembled water intake and construction method thereof

The invention discloses a marine underwater assembled water intake, which comprises a foundation trench which is formed on the bottom surface of the sea and at least two box culverts which are fixed in the foundation trench side by side, wherein a side plate of each box culvert is provided with a water inlet and a through hole; a side plate of one of the box culverts is provided with a water outlet; the through holes of two adjacent box culverts are in butt joint with each other; the upper surface of a top plate of each box culvert is provided with a watertight shutter which extends upwards; the watertight shutters of two adjacent box culverts are in butt joint with each other, and are then encircled into a cavity; a reinforced concrete connecting plate is arranged in the cavity; and a connecting reinforcement embedded in the top plate of each box culvert extends into the connecting plate. In the marine underwater assembled water intake, the lower part of each box culvert is fixed in the foundation trench, and the upper part of each box culvert is connected with the connecting plate into a whole through the connecting reinforcement embedded into the top plate of each box culvert, so that high stability is achieved, and wind wave resistance is enhanced. Simultaneously, the invention also discloses a construction method of the water intake.