This paper investigates the complex interaction between turbulent flow and a deep-water marine structure (overlapping circular cylinders) using a commercial computational fluid dynamics code applying the large eddy simulation approach. A number of three-dimensional large eddy simulations of wake flow around overlapping cylinders of finite heights are carried out for incoming flow Reynolds number in the range 1·0 × 104 to 1·0 × 105. The effect of the height of a circular mud mat having a fixed diameter and its effect on the turbulent flow and pressure fields around this kind of bluff body is investigated. The numerically computed results show some features of the complex separated flow structures and wake properties behind the cylinder. The simulated flow velocity field together with the bed material data can be used to evaluate and estimate the scour around the overlapping cylinder and assess its stability.