Four children and five adults were on a yacht that split in two when it collided with a launch north of Picton on Tuesday afternoon.
The vessels crashed between Picton Harbour and Waikawa Bay.
St John says two ambulances took five people with minor injuries and one with moderate injuries to Wairau Hospital.
Nicky Jenkins, from Coastguard Marlborough, says its rescue vessel arrived at the scene just a few minutes after the accident.
She says coastguard workers spent some time collecting debris from the yacht, so it wouldn't be a danger to other vessels.