The smallest ship I have cruised on was the old RCI Song Of America, 37,584 tons and max 1,575 passengers. Built in 19982 I cruised on her 12-15 1996 and 04-12-1998. She was the second ship I had been on.
I have great memories of cruising on her both times. On my bucket list is to go on her now as the Celestial Olympia for a Greek Island cruise.