This design is intended as a low cost introductory event for primary and secondary schools, after school clubs or individuals.

Using a ‘Windowlene’ bottle, a cheap cordless screwdriver, and other odds and ends you can make a swimming fish.


The flapping tail movement which propels the fish is achieved by rotating a bent wire through a slot within the hollow flexible tail.

The tail is made of strips of thin plastic sheet sandwiching a foam strip at the top and bottom edges so leaving a slot for the bent wire to run in.


The cordless screwdriver can be striped down to give a nice geared motor and rechargeable batteries, which can be sealed into the Windowlene body.


The end of the bent wire (from ring-main cable) can then be epoxied into the screwdriver end.


Add the fins, rearrange the handle to give the head and mouth and ballast it with plasticiene so it floats correctly and off you go!


For added refinement you can use a magnetically operated reed switch (eg an intruder alarm door switch) so that you can turn the motor on and off without having to break the seal into the bottle.