A volunteer lifeboat crew from Skegness was called out to the emergency at the weekend - in which two men were spotted drifting dangerously out into the North Sea.
The RNLI crew were alerted to the incident at about 11:20am on Saturday by UK Coastguard Humber based at Briddlington,
The video shows the crew racing out at some distance from the shore to reach the men, who did not seem to be aware of the danger they were in.
Lee St Quinton, RNLI Helmsman for Skegness RNLI Lifeboat, said: ‘On this occasion the gentlemen were very lucky that someone had alerted us to their plight.
"Inflatable boats and dinghys are not suitable for the open sea and should not be used where situations like this can evolve.
"In this case the people involved were not prepared for emergencies. There were no life jackets and no method of alerting anyone for help, save
for mobile phones which are not reliable out to sea."
The national RNLI tweeted the video to its 137,000 followers as an example of the dangers faced by those using inflatables at sea - especially in windy conditions.
They said: "Inflatables are are one of the most common reasons our crews and lifeguards get called into action. As was the case with @RNLIskegness who launched to these two people on board an inflatable over a mile out to sea in bad weather."
They added: "We strongly advise against using inflatables in the sea. Always use inflatables on a life-guarded beach, in between the red and yellow flags. Never use an inflatable when the orange windsock is flying. Never use an inflatable in choppy sea conditions."