The paper investigates the hydrodynamic behavior of *Escherichia coli* (E. coli) near solid boundaries, focusing on the circular trajectories observed for these bacteria. The authors provide a hydrodynamic model to explain this behavior, showing that the circular motion is a natural consequence of force-free and torque-free swimming, and the hydrodynamic interactions with the boundary. They compare the model's predictions with experimental data, finding reasonable agreement. The radius of curvature of the trajectory increases with the length of the bacterium. The model considers the bacterium as a rigid helix attached to a spherical body, and the boundary integral method is used to calculate the trajectory. The results show that the bacteria swim into the surface due to the hydrodynamic interactions, and the model can estimate the relationship between the bacterium's size and its distance from the surface. The study also discusses the influence of various geometrical parameters on the swimming behavior.The paper investigates the hydrodynamic behavior of *Escherichia coli* (E. coli) near solid boundaries, focusing on the circular trajectories observed for these bacteria. The authors provide a hydrodynamic model to explain this behavior, showing that the circular motion is a natural consequence of force-free and torque-free swimming, and the hydrodynamic interactions with the boundary. They compare the model's predictions with experimental data, finding reasonable agreement. The radius of curvature of the trajectory increases with the length of the bacterium. The model considers the bacterium as a rigid helix attached to a spherical body, and the boundary integral method is used to calculate the trajectory. The results show that the bacteria swim into the surface due to the hydrodynamic interactions, and the model can estimate the relationship between the bacterium's size and its distance from the surface. The study also discusses the influence of various geometrical parameters on the swimming behavior.