Study on water-entry of heavy objects is of great importance to practical application and theoretical modeling, as it is widely present in daily life, and many fields of engineering and science as well. Combining theoretical derivation with numerical simulations, we study the impact of the damping coefficient of water and the density of the rod on the water-entry dynamics of a uniformly distributed rod at low velocity. The dynamic differential equation is established according to Newton's second law of motion and the analytical solution is obtained, based on which numerical simulations are carried out and the motion characteristics of the rod is analyzed. Numerical results show that a rod with greater density than that of water will eventually reach a stable maximum sinking speed, which is proportional to the density difference between the rod and the water, and inversely proportional to the damping coefficient of the water. The greater the density difference, the longer it takes to reach the maximum sinking speed. However, when the density difference is small, the velocity of the rod reaches a peak at first, and then it decelerates and gradually approaches the final sinking speed. The formation of velocity peak is reasonably accounted based on the forces acting on the rod and thus its acceleration variations. On the contrary, if the density of the rod is less than that of the water, it will eventually suspend in the water at still. Results also show that the smaller the damping coefficient of water, the longer it takes for the rod to reach the maximum sinking speed, and vice versa. The effect