A tidal barrier, comprising: (a) a net having a tensile membrane, the tensile membrane having an upper edge and a lower edge, the lower edge having a plurality of anchor points which in use affix the lower edge to a seabed below a body of water; (b) a bladder affixed to the upper edge and having a valve via which the bladder is selectively inflatable or deflatable, the bladder having a sufficient volume to bias the upper edge of the tensile membrane to rise to a surface of the body of water when the volume is inflated with a gas; (c) a pump disposed in proximity to the tensile membrane with a controller which in use selectively prompts the pump to pump the gas, the tidal barrier further characterized by: a tank in fluid communication between the pump and the valve of the bladder, the pump being adapted to pump to the tank an amount of gas for inflating the volume of the bladder, the tank being adapted to store the gas pumped to it from the pump, and the tank having an output valve in fluid communication with the valve of the bladder and adapted to release the stored amount of gas to the bladder in response to a control input, and the pump including a floatation system comprising a floatation assembly that floats on the body of water and a structure connected to the floatation assembly, a cylinder with one end affixed to the seabed of the body of water, via a permanent foundation system, a piston comprising a shaft with a top end and a bottom end and a head disposed in the cylinder, the top end of the shaft being connected to the structure and the bottom end of the shaft being affixed to the head such that the floatation system actuates the piston in response to tidal changes in the body of water, a valve arranged at the cylinder, and a pipe connected with the valve and with the tank, wherein the floatation assembly actuates the piston within the cylinder to compress air or other gas, such that the compressed air or gas is discharged through the valve and the pipe to the tank. (a) a net having a tensile membrane, the tensile membrane having an upper edge and a lower edge, the lower edge having a plurality of anchor points which in use affix the lower edge to a seabed below a body of water; (b) a bladder affixed to the upper edge and having a valve via which the bladder is selectively inflatable or deflatable, the bladder having a sufficient volume to bias the upper edge of the tensile membrane to rise to a surface of the body of water when the volume is inflated with a gas; (c) a pump disposed in proximity to the tensile membrane with a controller which in use selectively prompts the pump to pump the gas, the tidal barrier further characterized by: a tank in fluid communication between the pump and the valve of the bladder, the pump being adapted to pump to the tank an amount of gas for inflating the volume of the bladder, the tank being adapted to store the gas pumped to it from the pump, and the tank having an output valve in fluid communication with the valve of the bladder and adapted to release the stored amount of gas to the bladder in response to a control input, and the pump including a floatation system comprising a floatation assembly that floats on the body of water and a structure connected to the floatation assembly, a cylinder with one end affixed to the seabed of the body of water, via a permanent foundation system, a piston comprising a shaft with a top end and a bottom end and a head disposed in the cylinder, the top end of the shaft being connected to the structure and the bottom end of the shaft being affixed to the head such that the floatation system actuates the piston in response to tidal changes in the body of water, a valve arranged at the cylinder, and a pipe connected with the valve and with the tank, wherein the floatation assembly actuates the piston within the cylinder to compress air or other gas, such that the compressed air or gas is discharged through the valve and the pipe to the tank. a tank in fluid communication between the pump and the valve of the bladder, the pump being adapted to pump to the tank an amount of gas for inflating the volume of the bladder, the tank being adapted to store the gas pumped to it from the pump, and the tank having an output valve in fluid communication with the valve of the bladder and adapted to release the stored amount of gas to the bladder in response to a control input, and the pump including a floatation system comprising a floatation assembly that floats on the body of water and a structure connected to the floatation assembly, a cylinder with one end affixed to the seabed of the body of water, via a permanent foundation system, a piston comprising a shaft with a top end and a bottom end and a head disposed in the cylinder, the top end of the shaft being connected to the structure and the bottom end of the shaft being affixed to the head such that the floatation system actuates the piston in response to tidal changes in the body of water, a valve arranged at the cylinder, and a pipe connected with the valve and with the tank, wherein the floatation assembly actuates the piston within the cylinder to compress air or other gas, such that the compressed air or gas is discharged through the valve and the pipe to the tank.