Robertson said the vessel capsized while it was in the Stella Passage, one of the harbour's main shipping channels.
The distress call that came through was a "PAN-PAN", which means a vessel is in an urgent situation but no one's life is in immediate danger.
"It's not a mayday, but it's a step down from a mayday.
"One of the concerns at the time was that there was a vessel that was going to be going through there, a big container ship."
Robertson said the 223-metre ship was of such a size "they definitely can't just hit the brakes".
Container ship Maersk Bogor was due to arrive at the Port of Tauranga at 8.05pm.
It was lucky the coastguard was already on the water and was able to make it to the Sledge within a couple of minutes.
The coastguard towed the Sledge away so the ship could pass, then returned the ship to the passage to right the boat before it came to shore.
Yesterday, the vessel was floating in the shallows in from of the Tauranga Yacht and Powerboating club.
The club posted a photo of the Sledge being pulled to shore in the comments of their social media post about the race.
The boat's skipper John Minnee helped take the boat out of the water.
Minnee said he was just glad no one was hurt.
"At least we're alive."