I am one of the few people who have not only fished from a cruise ship, but also caught something. 2003 on a Panama Canal crossing. My first cruise. We were on a balcony starboard side. First thing when we unpacked our suitcases, I expanded a telescoping fishing rod, threaded the line through the guides and attached a shiny fish lure. I leaned it against the balcony railing so the lure would swing in the wind or rock with the boat. I did hear people gossip about seeing it from outside viewing areas up above.
It was going to be impossible to fish from the balcony due to the lifeboats below. So after searching the ship for a suitable place I found the perfect deck. The Prominade deck. I think it was deck 5. This is the deck you could walk around the entire ship.
The ship moves pretty fast. Too fast for trolling. And if you hooked something at that speed it would spool you very quickly. So I figured it would have to be at a port. I got my chance at Aruba. We were leaving later in the evening. I stealthily brought the rod and reel downstairs. I didn't know if it was against the Ship's policy to fish from the ship, but didn't ask either. My sister said that I was going to get thrown in the ships jail (Brig?) Anyway, I used a lure called a Buzz Bomb. It's a jigging lure. This one was painted so that it glowed in the dark. They had some very bright 220volt flood lights that I dangled the lure in front of to get a good glow.
I dropped it down into the water from 20 feet above. I did have one couple who walked on by who asked "Are you doing what we think you are doing?", Yes.
I also had a ship crew member ask if i had caught anything. I worked the jig up and down and had a hit. I wasn't big. It looked to me like a small rockfish about 10 inches long and light orange in color. I unhooked and dropped the fish back in the water That was it for that trip.
I also fished for a short time on the stern while anchored off of Cabo on another cruise.. No bites there.
So to answer you, yes, it has been done. A telescoping rod fits nicely into your suitcase. Don't forget the reel and some artificial lures . Might be hard to secure bait, Ii would make the contents of your luggage stink. Fish from a cruise ship at your own risk. It's up to you to find out if it is legal or against ship policy.