A method for placing on a seabed a device carrying at least one equipment, the device comprising: - a first and a second bases (11, 12) secured together and forming two independent flotation spaces, - water/air inlet/outlet ports (14, 14', 15, 15') and control means for controlling the water and air flows inside the flotation spaces, at least one of the two bases (11, 12) carrying the equipment, the method comprising: - a step of filling the second base with water, the first base, emerged and floating on the surface, stabilizing the device during the immersion of the second base until contact with the seabed, - a step of filling the first base with water, the second base being in contact with the seabed and stabilizing the device during the immersion of the first base to the seabed, wherein the device satisfies the following conditions, at the moment the second base is landed on the seabed, the first base submerges completely: P 1 A. z G 1 − Z B 1 + y G 1 − y B 1 < Pim 2 y L 21 − y R 2 and P 1 A. z G 1 − Z B 1 − y G 1 − y B 1 < Pim 2 y R 2 − y L2 2 A being equal to 0.21, or 0.12 or 0.087 or 0.052, where, for a direct Cartesian reference system XYZ and the coordinates of any point M being noted x M, y M, z M: - G1 is the center of inertia of the masses of a first group defined by the first base, the equipment, and including the water inside the first base, the position of G1 being corrected for the free surface effects, - P1 is the emerged weight of the first group in the air, of value P1, - B1 is the hydrostatic thrust center of the first group, - R2 is the center of application of the immersed weight, of value Pim2, of the second group defined by the second base and its possible equipment, that is to say the resultant of the weight P2 of the second group and of the hydrostatic thrust of the second group, - L21 and L22 are the lateral bearing points of the second base on the bottom, in the case where the inclination occurs along the longitudinal axis X-X', with y L21 > y L22, the width being therefore greater than or equal to the difference y L21 - y L22. - a first and a second bases (11, 12) secured together and forming two independent flotation spaces, - water/air inlet/outlet ports (14, 14', 15, 15') and control means for controlling the water and air flows inside the flotation spaces, - a step of filling the second base with water, the first base, emerged and floating on the surface, stabilizing the device during the immersion of the second base until contact with the seabed, - a step of filling the first base with water, the second base being in contact with the seabed and stabilizing the device during the immersion of the first base to the seabed, - G1 is the center of inertia of the masses of a first group defined by the first base, the equipment, and including the water inside the first base, the position of G1 being corrected for the free surface effects, - P1 is the emerged weight of the first group in the air, of value P1, - B1 is the hydrostatic thrust center of the first group, - R2 is the center of application of the immersed weight, of value Pim2, of the second group defined by the second base and its possible equipment, that is to say the resultant of the weight P2 of the second group and of the hydrostatic thrust of the second group, - L21 and L22 are the lateral bearing points of the second base on the bottom, in the case where the inclination occurs along the longitudinal axis X-X', with y L21 > y L22, the width being therefore greater than or equal to the difference y L21 - y L22.