The numerous saline estuaries situated throughout Prince Edward Island permit high tides to carry salt water a long way inland and to penetrate the bedrock aquifer. Very little groundwater consumption occurs around the banks of the Eliot River estuary, yet salt water has moved into the bedrock and created a large zone of diffusion. This salty water extends as far as 1200 ft inland and has penetrated to a depth of 185 ft. Beneath this salty water is fresh groundwater, which extends down to about 600 ft where it is underlain by salty water.The salty water in the upper 185 ft of the aquifer is not separated from the fresh groundwater by a confining stratum, but is kept in this position by the higher head of the fresh groundwater. This head maintains a dynamic equilibrium with the heavier salty water. The effect of density in maintaining the position of a fresh and salt water front is not as important as has been previously thought.

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