Gary Patrick Hillier Smith (37) travelled to Jersey on the Condor Liberation earlier this year, when drugs were discovered during a search.
In total, the car contained 12 kilos of cannabis worth between £180,000 and £240,000 and 20 10ml bottles of testosterone propionate.
He admitted two charges of importing illegal drugs and originally said he was stashing them and was going to take them back to the UK.
However, he later admitted he was intending to supply them and was jailed for 4½ years.
Delivering the sentence of the Royal Court, the Bailiff, Sir William Bailhache, said: ‘It seems to us that it is clear the defendant was the organiser of this importation and he intended to sell them when he arrived in the Island.
‘We are not very satisfied the defendant showed much remorse.’
Crown Advocate Conrad Yates, prosecuting, said that on the evening of 5 May, Smith was the rear-seat passenger of a Ford Focus sitting next to his son with his partner driving.
They told Customs officers they had been to the Island before and were staying at the Hotel de Normandie and visiting the boat show.
While in the search bay a drug detector dog was brought out and it showed heightened interest around the door areas.
A physical search took place, and officers found vacuum-wrapped packages of drugs behind the trim panel of a door. Smith and his partner were immediately arrested.
She said she had no knowledge of the drugs and Smith told officers: ‘She knows nothing about it. It was all me. I put it in there.
‘They are in both rear doors and the front passenger door.’
Later he said: ‘It’s my own stash. I should have taken it out before I came over. I wasn’t smuggling it.’
During the search several mobile phones were also seized, along with empty UK SIM card packs.
Smith claimed he had a chance meeting in Southampton with a man known as ‘Des’ or ‘D’, who was trying to offload £7,000 worth of drugs.
The man let Smith take the drugs ‘on tick’ and he subsequently stashed them behind the door panels for safekeeping. He said he had previously travelled to Jersey without a car and it did not cross his mind to remove the drugs before travelling.
His partner said she had no knowledge of the drugs and after no evidence was found against her she was released and returned to the UK with their child.
Smith denied the police access to his phone by refusing to give them the PIN code.
Crown Advocate Yates said: ‘It is clear he accepts his intention to sell drugs on to discharge his and his partner’s debts.
‘This was a commercial importation into the Island destined for the local market.’
Advocate James Bell, defending, said his client wished to apologise to the court for a ‘serious error of judgement’.
He said his client admitted his responsibility to Customs officers and he was co-operative.
He added: ‘He regrets his actions and the impact on the Island, not just because he was caught, and he apologies for taking up the court’s time.
‘He sees he made a mistake by getting involved in this enterprise.’
He added that his client had a long history of mental-health problems, had previously been diagnosed with schizophrenia and his partner’s financial position at the time was the reason he became involved in importing drugs.
The Jurats in the case were Geoffrey Grime, Kim Averty, Anthony Olsen, Jane Ronge and Elizabeth Dulake.