They were taken to hospital for specialist care at the regional burns centre after the incident on Monday evening.
It happened at around 6.40pm on Monday, August 3 on a river cruising boat near the Sandy Lane Industrial Estate in Stourport on Severn.
Two ambulances, a paramedic officer, the Midlands Air Ambulance critical care car and the Midlands Air Ambulances from Cosford and Stensham were sent to the scene.
A West Midland Ambulance Service spokesman said: “On arrival, crews found the man and woman who had been on board doing exactly the right thing – they were using lukewarm water to cool the burns.
“The woman was suspected of being the slightly more serious of the two.
"After assessment and treatment at the scene she was taken to Queen Elizabeth Hospital Birmingham by ambulance. One of the critical care paramedics from the air ambulance travelled with the crew.
“The man was also assessed and treated at the scene. He too was taken by ambulance to the same hospital, again with a critical care paramedic travelling with the ambulance crew.”