An underwater propulsion device comprising: (a) a foot board; (b) a battery sealed in a watertight compartment (4303A, 4303B) that is integrated with said foot board; (c) wherein said foot board comprises two portions (4205A, 4205B), each with an attachment structure for one of said user's feet, and wherein said portions (4205A, 4205B)are connectable to one another by a linkage that permits said portions (4205A, 4205B) to pivot relative to one another; (d) wherein said device has two battery-powered underwater propulsion units (4211A, 4211B); and wherein the first of said propulsion units is mounted on the first of said portions of said foot board and the second of said propulsion units is mounted on the second of said portions of said foot board; and wherein each of said portions (4205A, 4205B) of said foot board has at least one integrated battery in it that is connected by a watertight connection to the one of said propulsion units (4211A, 4211B) that is mounted on that portion (4211A, 4211B) of said foot board; (e) a throttle control system integrated with said foot board that allows the throttle of said propulsion unit (4211A, 4211B) to be controlled by a swivel movement of said user's foot, wherein at least one of said foot attachment structures comprises a foot pedal mount that fixes one end of said user's foot to said foot board about a rotational axis that allows the opposite end of said user's foot to swivel from side to side; and wherein said throttle control system further includes a spring return which tends to bring said user's foot to neutral position when said user does not exert any swivel force with their foot. (a) a foot board; (b) a battery sealed in a watertight compartment (4303A, 4303B) that is integrated with said foot board; (c) wherein said foot board comprises two portions (4205A, 4205B), each with an attachment structure for one of said user's feet, and wherein said portions (4205A, 4205B)are connectable to one another by a linkage that permits said portions (4205A, 4205B) to pivot relative to one another; (d) wherein said device has two battery-powered underwater propulsion units (4211A, 4211B); and wherein the first of said propulsion units is mounted on the first of said portions of said foot board and the second of said propulsion units is mounted on the second of said portions of said foot board; and wherein each of said portions (4205A, 4205B) of said foot board has at least one integrated battery in it that is connected by a watertight connection to the one of said propulsion units (4211A, 4211B) that is mounted on that portion (4211A, 4211B) of said foot board; (e) a throttle control system integrated with said foot board that allows the throttle of said propulsion unit (4211A, 4211B) to be controlled by a swivel movement of said user's foot, wherein at least one of said foot attachment structures comprises a foot pedal mount that fixes one end of said user's foot to said foot board about a rotational axis that allows the opposite end of said user's foot to swivel from side to side; and wherein said throttle control system further includes a spring return which tends to bring said user's foot to neutral position when said user does not exert any swivel force with their foot.