Ice trays work great... IF you only need ice for a few drinks, the next day, and have lots of room in the freezer
to lay the trays out flat while they're freezing. Many marine
freezers don't get much below freezing, unlike home freezers which get down to 0F. It could take a very long time to freeze a tray full of ice.
I am limited on space, too, but the countertop ice maker is well worth the room it takes up. I bring it out, make a one-gallon bag or two full of ice, stuff the bags in the freezer
and then stow the ice maker. I do this when it's convenient and power
is available. It runs fine off the inverter
, so even underway in settled conditions works.