Alison Whelan, 51, and friend Tristam Locke were under the influence of drugs and alcohol when they climbed onto the moored 100-seater Dart Princess in Dartmouth, Devon on September 10, 2011.
Whelan dialled 999 and and said she thought she was having a seizure. Paramedics arrived and found the defendant "rambling", while Locke became abusive and pushed one of the medics over.
Shortly before police arrived at the scene, Whelan unmoored the 45ft vessel and started drifting away, shouting "I'm A Pirate" and "I'm Jack Sparrow" - Johnny Depp's character in the Pirates of the Caribbean franchise.
Whelan told police she untied the ropes because she kept tripping over them and "before she knew it" she felt the boat moving and "noticed the hotels getting a long way away".
The boat hit other vessels "like a pinball machine", including a £70,000 catamaran, and only came to a stop an hour later and a mile upstream, where lifeboats towed the pair back to the harbour to be arrested.
Whelan, who told officers she "would have ended up in St Tropez" if she hadn't been caught, pleaded guilty to aggravated vehicle taking and was jailed for 122 days at Torquay Magistrates Court.
Thousands of pounds worth of damage was caused, including £1,500 to the ferry itself and £300 to a moored vessel called Tomcat. Over 30 ambulance, police, coastguard and RNLI officers were involved in the operation.
Locke was fined £100 in a separate court case last year for assaulting the ambulance technician.