A large tree swept past as the horses huddled for safety.

Watching her horses stranded in the middle of raging floodwaters as daylight faded, Beth Ferguson felt like she was seeing a nightmare unfold before her eyes.

The South Canterbury woman and her husband, Ben, considered donning wetsuits and wading into the floodwaters on their Hakataramea Valley farm to save the horses and miniature pony, which were stranded on an island in what had hours earlier been a dry creek bed.

But with large pieces of debris rushing past, the pair just couldn't risk it.

SUPPLIED Horses stranded by floodwaters in the Hakataramea Valley.

"We were starting to really panic, we were running out of daylight," Ferguson said.

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"We were just imagining the horses being wiped out."

The pony and one of the four horses were still trying to escape the raging floodwaters.

Luckily, the appearance of a "humungous" tree being swept down the torrent was enough to spook the horses into making a dash towards the bank.

"I swim the big horses in summer so they're really capable, but my little mini, Thunder, didn't know what to do," she said.

"She was pretty lucky one of the big horses led her out."

They captured the dramatic dash to safety on video.