Floating bloody office blocks
Take a 1960's high rise office block. Rotate through 90 degrees. Pack it with the overpaid, over weight and unfortunately over here and you have a cruise liner.
EDIT: Ship I've found out since this a liner is something totally different.
Broadly speaking they are square. Many stories high, infected with e-coli and other bacterium. The one pictured right is actually quite pretty. Despite the risk of food poison, the price and the ugliness they've become unbelievably popular. We were in Aruba for 48 hours and we saw 8 liners.
At sea they clip along, to power that much flab along takes oomph. They're also maneuverable, to get in and out of small harbors. At night they are ablaze with lights, making the navigation lights completely inviable. They hare around, and since they're basically square and uniformly randomly lit its almost impossible to tell which way they're pointing and they come up on you awful fast. I don't like 'em - you can tell.
I count 24 balconies per deck in the section of side in that pic, with 5 decks of cabins. 2 per cabin and you've got 240 peoples worth of posh cabins in this small section. These things have thousands of people on them. Unfortunately they let them off too (the ones without food poisoning)