The ferry ride is at least 6 hours long. Any special techniques for keeping food cold.
In order to avoid defrosting our motorhome fridge, we turn it off on Sunday night when we go to bed and back on in the morning when we get up. Typically, we will start at about 35 degrees. 8 hours later, when we turn the fridge back on, the temperature will be 40 to 41. Ice cream and other frozen foods are still frozen.
You should be well within safe zones during your ferry trip. Good luck.