The National Weather Service says the twister began on the water, and made its way on land after 7 a.m. Friday traveling a mile and a half inland.
Sara Mai Kui recalled how powerful the waterspout looked as she watched it from the Kailua boat ramp.
She described the water coming off the shore creating what looked like a bowl of water.
But not long after, it made landfall, and she thought, "Oh, no! There's going to be another tornado, and it?s going to take somebody's house," Mai Kui said.
The twister came up on Mokulua Drive, destroying a vacation rental.
The winds pulled off up part of the roof and blew it into a neighbor?s yard, where it landed in an ironwood tree.
A friend of the property owner said a couple with an infant was vacationing at the home at the time. The couple had plans to fly to the neighboring islands, but changed their minds and extended their stay on Oahu.
"They left to go to Kauai, and because of the bad weather, they cancelled and came back here," said Darren DeMello.
The National Weather Service was on scene within hours.
"Based on what we saw on radar, it was enough for our office to send me out to take a look at what actually caused this wind-related damage," said meteorologist Mike Cantin.