A submerging air pressure projectile launching toy, suitable for use by children, includes a main device body, a launch structure connected to an upper end thereof to define an interior air chamber, and a projectile, all for use in water. The main device body has a hollow elongate member, defining a longitudinal axis, and a water intake, in fluid communication with the interior air chamber, at a lower end thereof, and the water intake opening is perpendicular to the longitudinal axis. The projectile is temporarily mountable via to the launch structure to semi-seal the interior air chamber. When the lower end of the main device body is pushed into a body of water, air within the interior air chamber is compressed until a frictional or other coupling force between the projectile and the launch structure is overcome, causing the projectile to launch into the air.