Fizzy Sub

A one-person, plastic minisub or dinky boat powered by a large replaceable canister of baking powder at the back. The sub or boat must be styled to look as if it came out of a cornflake box.

The baking powder is introduced little by little into a mixing chamber by a gravity fed valve. A nozzle directs the resulting fizz backwards. Optional turbo-boost can be provided by squirting lemon juice or vinegar into the mixing chamber.

Only minimal steering will be necessary as this is only intended for pootling around in shallowish waters. A rudder with foot controls as used on some canoes/kayaks would suffice. Alternatively, the outlet nozzle could be manouverable.

For the sub, diving could be acheived by a simple system of weights which could be jetisoned when you wish to resurface. Another method could be to counteract the weights by flooding the baking powder canister when it is nearly empty to increase fizzing and bob the sub up to the surface. The initial weight of the baking powder will also help you to sink.

An added advantage is that baking powder is slightly on the alkaline side of neutral and experts are worried about the rising acidity of the earth's oceans, caused by the the increasing amounts of carbon dioxide in the atmosphere. So you would be helping, in a small way, to redress the balance.