Penarth RNLI’s D Class lifeboat came across the 20ft motor vessel near Lavernock Point during a routine training exercise.
The skipper was unable to raise the anchor, and the vessel began drifting toward Sully Island in the fast-ebbing tide.
A crew member boarded the vessel and freed the anchor, allowing the boat to continue safely under its own power.
RNLI volunteers then escorted the vessel toward Cardiff Bay, before returning to the station.
A spokesperson for RNLI Penarth Lifeboat Station said: “Our lifeboats were on routine exercise this morning when our D Class went to the aid of a vessel in difficulty near Lavernock Point.
“Our crews were just completing their training when the D Class encountered a 20ft motor vessel with a family of 4 aboard.
“The skipper was unable to raise the anchor and the vessel was dragging in the fast ebbing tide towards Sully Island.
“A crewmember was put aboard, and the anchor was quickly raised.
“Our lifeboats then escorted the vessel, which was able to to make way under its own power, towards Cardiff Bay.
“Our volunteers were able to return to station to rehouse the lifeboats”.
