A device for transferring rotational, mechanical motion into sinusoidal wave-like motion, said device comprising: a. at least one motor, generating rotational movement around a first Cartesian axis; and b. an elongated rod, curved in the form of a helix, substantially aligned along said first Cartesian axis, and rotated by the at least one motor; characterized in that said device further comprises: c. a surface comprised of discrete, connected hollow elements, wherein: i. the curved rod is interlaced within the said discrete hollow elements, such that the surface is undulated, and the rotation of the curved rod dynamically changes the surface's shape, moving the discrete hollow elements along a second perpendicular Cartesian axis, thus creating a wave like motion; ii. the width of each said discrete hollow element is slightly larger than the diameter of the helix-shaped rod, so as while rotating, the elongated rod is freely movable within the cavity of the discrete hollow elements, along the third perpendicular Cartesian axis; iii. the said surface interacts with the surrounding medium or base-surface upon-which the device is moving, wherein said interaction is generated by said wave-like motion, such that the said interaction creates a propelling force that drives said device forward or backward along the said first Cartesian axis. a. at least one motor, generating rotational movement around a first Cartesian axis; and b. an elongated rod, curved in the form of a helix, substantially aligned along said first Cartesian axis, and rotated by the at least one motor; characterized in that said device further comprises: c. a surface comprised of discrete, connected hollow elements, wherein: i. the curved rod is interlaced within the said discrete hollow elements, such that the surface is undulated, and the rotation of the curved rod dynamically changes the surface's shape, moving the discrete hollow elements along a second perpendicular Cartesian axis, thus creating a wave like motion; ii. the width of each said discrete hollow element is slightly larger than the diameter of the helix-shaped rod, so as while rotating, the elongated rod is freely movable within the cavity of the discrete hollow elements, along the third perpendicular Cartesian axis; iii. the said surface interacts with the surrounding medium or base-surface upon-which the device is moving, wherein said interaction is generated by said wave-like motion, such that the said interaction creates a propelling force that drives said device forward or backward along the said first Cartesian axis. i. the curved rod is interlaced within the said discrete hollow elements, such that the surface is undulated, and the rotation of the curved rod dynamically changes the surface's shape, moving the discrete hollow elements along a second perpendicular Cartesian axis, thus creating a wave like motion; ii. the width of each said discrete hollow element is slightly larger than the diameter of the helix-shaped rod, so as while rotating, the elongated rod is freely movable within the cavity of the discrete hollow elements, along the third perpendicular Cartesian axis; iii. the said surface interacts with the surrounding medium or base-surface upon-which the device is moving, wherein said interaction is generated by said wave-like motion, such that the said interaction creates a propelling force that drives said device forward or backward along the said first Cartesian axis.