OK, a bit niche, but it might be of interest to someone else.
Back in 2019 we visited Norway and Iceland with Cunard and I had a day's scuba diving booked in Reykjavik that fell through on the day and left me dockside twiddling my thumbs. Then I spotted our sommelier, in his civvies, cycling away from Queen Vic and he stopped to say hello. Turns out Cunard have (Had, post covid?) bikes aboard for crew use so I went to the Purser's desk to see if I could borrow one. No, crew use only. So I went into town and hired a half-decent little Trek hybrid and had a lovely morning pottering around. As I was freezing my toes on a paddle in the wrong bay, the geothermally heated water is in the next bay along, I wondered if I could take my own bike next cruise.
Yes, says the Cunard website, provided it's a folding bike, or a bike that can be disassembled, that bikes can be used on land only (No hooning around Deck 3!) and that I had to take it on and off the ship myself. A folding bike was obviously going to be the most practical solution, so I bought a folding bike off ebay, £44, and a carry bag, £18, and for less than the cost of a standard sightseeing trip I was set.
Our cruise this year was also Norway and Iceland, and the bike went on board in its carry-bag with the rest of the luggage. I simply dropped it off with the cases and it was delivered to the cabin door. Sorry, stateroom door. We were in Queen's this time, so had a space where it sat all fortnight without getting in the way. It would fit in any cabin, it's no bigger than a standard suitcase when folded. And no it isn't a Brompton, which would fold even smaller but would be way more expensive to buy.
Getting the bike off the ship to ride was easy. Take bike out of bag, still folded, carry downstairs and wheel/carry down gangway. The security staff didn't bat an eyelid. Then unfold dockside and ride away.
I'd done a bit of pre-cruise research to sort out where I wanted to visit, but that was fun in itself. The only thing I'd forgotten was somewhere on the bike to stow a bottle of water, I like to visit more remote spots that tend to be cafe free, but I can sort that before the next cruise.
I thought getting back aboard might be less straightforward, but it was actually very simple. I folded the bike dockside and wheeled it up the gangway, where a pleasant security man held out a hand and pulled it under the security tapes whilst I went through security checks as normal, then he handed it back to me to take to the stateroom. Note that I had a tool bag strapped behind the saddle for a mini-pump, a couple of spare inner tubes, tyre-levers, spanner to get the wheels off and a chain tool, all the basic stuff, but wasn't asked about them at all.
As the lifts were quiet I took the bike back up in the lift and then put it back in the bag until next time.
Come disembarkation I put a luggage tag on the bike bag as I had coming aboard, put it out with the cases and collected land-side with the rest of the luggage
Overall, a totally stress-free experience. Well done Cunard.