The first incident took place at around 2pm when the skipper of dive boat ‘Scimitar’ alerted coastguards to a male diver in difficulty off the west coast of Portland.
The rescue helicopter flew the man to Poole where he was met by a dive doctor and quickly taken to a nearby recompression chamber.
Later on Saturday, the rescue helicopter airlifted another diver from Lulworth Cove.
Earlier the same day, coastguards were called after a man had fallen onto the pontoon in Weymouth Harbour and injured himself.
The incident took place at around 4.40am.
The alarm was raised by a person on board a boat nearby.
Dorset police also attended. The man was treated by paramedics.
At around 7pm, coastguards were called to help a woman who was stung by an unknown substance in the sea at Bournemouth Beach.
Ambulance crews attended to help the woman at around 7pm.