He likened the many contained aquifers to veins of a body or underground hosepipes, carrying water long distances securely.
Outside Hawke's Bay Prison at Mangaroa he pointed out a bore to an aquifer that flowed under the Tukituki River and Cape Kidnappers Golf Course on its way out to sea.
He was certain of its course because of matching gravels found when drilling, but where other aquifers came from or went to required "a bit of guess work".
He said Hawke's Bay Regional Council needed to do more exploratory drilling because there was a lot more water underground but it needed to be found and qualified/quantified to "open up the resource to everyone".
The tour group was a mix of private and public sector leaders, invited by Napier MP Stuart Nash.
"I think it is very important the region's leaders understand what is happening," he said.
"I'd like them to put pressure on the Regional Council so it can do some research around this. The level of data and research we are doing is not sufficient to provide us with informed decisions on how we use our water."