Just to let you know ALDI is selling a 12V dehumidifier, which may be suitable for your boat or caravan.
Max capacity 400ml/day, Peltier design, 2.2kg (all information from memory). It is supposed to run on 240V and comes with a 6Amp/13.5V converter. You would have to plumb your own drain into the collection tank for prolonged use.
Probably a bit over-priced at £39.99, as it is only an inside-out coolbox without the insulation but at a quarter of the weight of the smaller condensing dehumidifiers, at least it won’t sink the boat.