A mutually opposite generally horizontal gravity-driven flow water toy including at least first and second water inlets, at least first and second generally vertical water conduits coupled to respective ones of the at least first and second water inlets for directing a gravity flow of water therethrough from the respective ones of the first and second water inlets, at least first and second generally horizontal water conduits coupled to respective ones of the at least first and second generally vertical water conduits for directing a gravity flow of water therethrough from the respective ones of the first and second water inlets and via respective ones of the at least first and second generally vertical water conduits, the at least first and second generally horizontal water conduits being arranged such that the gravity flow of water therethrough is in generally opposite directions.

A mutually opposite generally horizontal gravity-driven flow water toy including at least first and second water inlets, at least first and second generally vertical water conduits coupled to respective ones of the at least first and second water inlets for directing a gravity flow of water therethrough from the respective ones of the first and second water inlets, at least first and second generally horizontal water conduits coupled to respective ones of the at least first and second generally vertical water conduits for directing a gravity flow of water therethrough from the respective ones of the first and second water inlets and via respective ones of the at least first and second generally vertical water conduits, the at least first and second generally horizontal water conduits being arranged such that the gravity flow of water therethrough is in generally opposite directions.

A combination aquatic toy and a reservoir wherein the reservoir comprises a container to contain a body of water and a contactless electrical power transfer transmitter, the toy is a submersible or is submersible and comprises a body carrying a battery and a battery powered propeller (fin or screw propeller or foil or impeller or other) to drive the toy through the body of water and contactless power transfer receiver to receive power, when in sufficient proximity to the transmitter, from the transmitter.

A combination aquatic toy and a reservoir wherein the reservoir comprises a container to contain a body of water and a contactless electrical power transfer transmitter, the toy is a submersible or is submersible and comprises a body carrying a battery and a battery powered propeller (fin or screw propeller or foil or impeller or other) to drive the toy through the body of water and contactless power transfer receiver to receive power, when in sufficient proximity to the transmitter, from the transmitter.

Provided herein is a fish robot. The fish robot includes a head unit corresponding to head portion of a fish; a driving unit coupled to the head unit to generate driving force by sinusoidal swimming movement; a waterproof cover coupled to the head unit with elasticity in which the driving unit being inserted to be sealed; and a body unit coupled to the head unit with elasticity corresponding to body portion of the fish in which the waterproof cover being inserted to be supported.

Provided herein is a fish robot. The fish robot includes a head unit corresponding to head portion of a fish; a driving unit coupled to the head unit to generate driving force by sinusoidal swimming movement; a waterproof cover coupled to the head unit with elasticity in which the driving unit being inserted to be sealed; and a body unit coupled to the head unit with elasticity corresponding to body portion of the fish in which the waterproof cover being inserted to be supported.

An apparatus or educational toy comprising a main body (120, 220, 320, 520) and a drive mechanism (140, 240, 340, 540), wherein the drive mechanism (140, 240, 340, 540) comprises a reservoir (142, 242, 342) for storing a driving liquid, a discharge outlet (144, 244a, 244b, 344, 544a, 544b) through which the driving liquid is discharged from the main body (120, 220, 320, 520) to generate a driving thrust, a liquid delivery path (146, 246a, 246b, 346) for delivering the driving liquid for a reservoir outlet (148, 348, 448) to the discharge outlet (144, 244a, 244b, 344, 544a, 544b), and a threshold setting device (147, 347); and wherein the threshold setting device (147, 347) sets a threshold thrust level so that the driving liquid is to pass from the reservoir (142, 242, 342) and discharged from the discharge outlet (144, 244a, 244b, 344, 544a, 544b) upon reaching the threshold thrust level during operation.

An apparatus or educational toy comprising a main body (120, 220, 320, 520) and a drive mechanism (140, 240, 340, 540), wherein the drive mechanism (140, 240, 340, 540) comprises a reservoir (142, 242, 342) for storing a driving liquid, a discharge outlet (144, 244a, 244b, 344, 544a, 544b) through which the driving liquid is discharged from the main body (120, 220, 320, 520) to generate a driving thrust, a liquid delivery path (146, 246a, 246b, 346) for delivering the driving liquid for a reservoir outlet (148, 348, 448) to the discharge outlet (144, 244a, 244b, 344, 544a, 544b), and a threshold setting device (147, 347); and wherein the threshold setting device (147, 347) sets a threshold thrust level so that the driving liquid is to pass from the reservoir (142, 242, 342) and discharged from the discharge outlet (144, 244a, 244b, 344, 544a, 544b) upon reaching the threshold thrust level during operation.

A projectile for launch in a body of water is described herein. The head of the projectile may be soft, the projectile may have a total specific gravity greater than about 0.95, the center of gravity may be located nearer the front end of the projectile as compared to the rear end and/or the length of the projectile relative to the maximum diameter may be greater than about 7:1. Methods of launching the same are also described herein.

A projectile for launch in a body of water is described herein. The head of the projectile may be soft, the projectile may have a total specific gravity greater than about 0.95, the center of gravity may be located nearer the front end of the projectile as compared to the rear end and/or the length of the projectile relative to the maximum diameter may be greater than about 7:1. Methods of launching the same are also described herein.