Pam and Alan Lawson had been chopping firewood outside one of these properties, and were first on the scene.
Neither had seen the crash. They were both wearing earmuffs with chainsaws going so all they heard was a "thump", Mrs Lawson said, before they noticed a wet patch further along the road.
"We looked over [at the drain] and we looked down and saw this car, and we thought, when it landed it would have splashed up the water," she said. "When we saw the car, panic stations started then."
The drain was wide, with the water surface below road level.
"We couldn't do anything, we couldn't get in there. We couldn't get into any of the doors because it was facing down. All we could do was yell out and wait to see if we heard anything.
"I was yelling out to say 'make a noise, or bang on the car if you can hear', but we didn't hear anything."
The pair ran to nearby houses to get help and call the emergency services.
Mrs Lawson said she felt for the family who had lost a loved one.
Yesterday's fatal crash brings the region's road toll, from Wairoa to Tararua, up to 19 - six more than the total number of fatalities for the region last year.
Of the 18 previous fatalities in the Hawke's Bay districts this year, eight were drivers, three were passengers, two were motorcyclists, two were cyclists and two were pedestrians.
Already the 2017 road toll is the highest in three years. Last year there were 13 road fatalities in the Wairoa, Hastings, Central Hawke's Bay and Tararua districts and Napier City - four down on the area's 2015 toll of 17.
In the Police Eastern District area - which includes Gisborne and Hawke's Bay, but not Tararua - there have been 24 fatalities this year. There were 13 last year.