Water cooled
I installed a water cooled refrigerator on my boat to avoid the air circulation problem. I had installed an air cooled one on a previous boat. You need very good air circulation for an air cooled unit. Living in the north this can be in the cabin. Some units come with duct work that mates to the unit. The specs on the unit should tell you how much cooling space is needed. Look for a good sized locker that you don't mind lossing, because you can't block the air circulation. Also figure on adding batteries as refrigerators use a lot of power.Ray Chapman