An underwater diver doesn't always require the whole flexibility provided by the SCUBA air system, especially when the diver is immersed in a small region for extended periods of time.
The "Hookah" (Surface Air Supply) was created specifically for such uses. No high-pressure air tanks, such as those carried on a diver's back, are used in the Hookah air system. Instead, it makes use of a surface-mounted compact air compressor.

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The air is given to the diver through a floating air hose and is driven by a 14 hp gasoline engine motor. The diver has an infinite supply of air with the Hookah system, which will only stop flowing when the engine or motor that drives the compressor stops working. When compared to the expense of replacing SCUBA tanks every hour or so, this results in a genuinely cost-effective air system that will rapidly pay for itself.