An anchoring device for an element floating on the surface of an expanse of water, such as a sea, comprising: - a lower portion, including a means for fastening to the bottom of the expanse of water and suitable for carrying out a strong fastening operation such that the anchoring device can no longer be moved relative to said bottom, characterized in that said device also comprises: - an upper portion, comprising an attachment means for at least two lines, said upper portion being attached to the lower portion using a connecting means that is rotatable around a substantially vertical axis of rotation, the attachment means comprising a ball joint, - a hollow body supporting the fastening means and the attachment means, each ball joint being formed by two serial pivot links (16A, 16B), with perpendicular axes, formed by first and second connecting elements, such that: • the first connecting element passes through a complementary opening formed in the hollow body, so as to form the first pivot link, and includes a first end, arranged inside the hollow body, provided with a shoulder intended to cooperate with an edge of the opening, and a second end, arranged at the end of the hollow body, comprising an opening for the passage of a shaft of the second pivot link, • the second connecting element comprises a first end including an opening for passage of the shaft of the second pivot link, and a second end supporting the line. - a lower portion, including a means for fastening to the bottom of the expanse of water and suitable for carrying out a strong fastening operation such that the anchoring device can no longer be moved relative to said bottom, - an upper portion, comprising an attachment means for at least two lines, said upper portion being attached to the lower portion using a connecting means that is rotatable around a substantially vertical axis of rotation, the attachment means comprising a ball joint, - a hollow body supporting the fastening means and the attachment means, each ball joint being formed by two serial pivot links (16A, 16B), with perpendicular axes, formed by first and second connecting elements, such that: • the first connecting element passes through a complementary opening formed in the hollow body, so as to form the first pivot link, and includes a first end, arranged inside the hollow body, provided with a shoulder intended to cooperate with an edge of the opening, and a second end, arranged at the end of the hollow body, comprising an opening for the passage of a shaft of the second pivot link, • the second connecting element comprises a first end including an opening for passage of the shaft of the second pivot link, and a second end supporting the line. • the first connecting element passes through a complementary opening formed in the hollow body, so as to form the first pivot link, and includes a first end, arranged inside the hollow body, provided with a shoulder intended to cooperate with an edge of the opening, and a second end, arranged at the end of the hollow body, comprising an opening for the passage of a shaft of the second pivot link, • the second connecting element comprises a first end including an opening for passage of the shaft of the second pivot link, and a second end supporting the line.