I'm pretty sure with the underwater air powered buzzer they are adjustable for the amount of air flow. Small adjustments change the pitch and tone of the buzzer. Should be pretty easy to make them drastically different for two or three playing areas in one pool.

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An aquifer is a water bearing layer of rock or soil. Aquifers are separated by impermeable layers of rock or clay called an aquitard. Aquitard, however may sound a bit offensive to some, and therefore we will be changing the name to Aquachallenge.