Two people were rescued by the RNLI after falling while walking on Hilbre Island.
The volunteer crew at West Kirby lifeboat were tasked at 11.12am on Saturday after the alarm was raised.
Both had slipped on rocks between the islands and one had seriously damaged her shoulder.
An off-duty nurse was in the vicinity and spotted the incident and immediately contacted HM Coastguard to request assistance and remained with the casualties until the volunteer crew arrived on scene.
West Kirby RNLI lifeboat was on an exercise nearby and upon reaching the casualties, the crew undertook a medical assessment of the casualties.
The pair were transported by the BV tractor to the station to carry out a further assessment and provide immediate medical care.
The injured casualty was taken to hospital for further treatment.
Richard Diamond, West Kirby RNLI Lifeboat Operations Manager said: “We can’t thank the passer-by enough for her quick decision-making and the care she provided before further help arrived.
“We would always encourage people to carry a means of communication when visiting Hilbre and the surrounding area and to phone 999 should they find themselves in any danger.”