Hand launchable hydrodynamic recreational device

A hydrodynamic recreational device comprising:

• a body including a nose region for confronting a body of water when the device is traveling through the medium, said nose region having in cross section defined by at least one plane passing through the device's travel path continuously smoothly contoured lines extending substantially symmetrically rearwardly from an apex defining a leading edge of the device to a tail region of the body, the lines in cross section being furthest apart at the approximate fore-to-aft center of the elongate body and positioned to give maximum stability when hand-launched,
• the body being substantially smoothly arcuately contoured from the leading edge to the tail region thereof to produce a drag coefficient of less than approximately 0.15 and the body being formed of one or more materials that produce in the body a specific gravity of between approximately 0.9 and 1.1 relative to a body of water in which the device may be made to travel by hand-launching the device.

A hand-launchable projectile for submarine movement within a body of water having a defined specific gravity, the projectile comprising:

• an elongate body having a long central axis, the body including a nose section defining a smooth continuous water-confronting surface, a generally cylindrical mid-section dimensioned to be grasped between at least semicircumferentially extending thumb and opposing fingers of a user's hand for launching the projectile and a tail section including plural arcuately spaced stabilizing fins projecting from the tail section radially in at least one plane containing the central axis of the body,
• the body having a predefined specific gravity that is substantially the same as, and within .+-.10% of, the defined density of such water, whereby the projectile when launched by hand within the water travels therein along a substantially straight-line trajectory of its launch.

A hand-launchable projectile for sustained submarine movement within a body of water having a defined specific gravity, the projectile comprising:

• a body including a nose section and a mid-section dimensioned to be gasped by a user's hand for launching the projectile, the body having a central axis, the body further including a tail section including plural arcuately spaced stabilizing fins projecting from the tail section radially in at least one plane containing the central axis of the body, the body being formed with a surface preparation that results in a drag coefficient of less than approximately 0.15,
• the body having a specific gravity that is substantially the same as, and within .+-.10% of, the defined specific gravity of the body of water, the body being dimensioned to have a characteristic length that produces a Reynolds number of flow within the body of water at a time when the body is launched by hand of less than approximately 5.0.times.10.sup.6, whereby the projectile when launched by hand exhibits neutral buoyancy and stability in sustained submarine movement.