A couple of years ago, myhusband and I did a 2 week cruise to celebrate our 40th wedding annivrersary. I found it pretty easy tto keep to low carb. Breakfast was a buffet type, so EASY to have a fry-up ! [ I did like American bacon] For lunch I often skipped and just had coffee, but a salad would have been simple to get. Even the 5 course dinners were Ok I just made sure that most of my choices were salads.
There was free ice cream on offer on the top deck every afternoon, but they had a superb sugar free strawberry one on the 2 or 3 occasions I had one.
It's just a question of knowing where those carbs are hiding. Remember that starchy foods are as high in carbs as sugary ones. Potatoes, rice, Pasta. bread and other baked goods; pastry. that's the risky bit also thickened sauces. Watch out for too much fruit too!
Safe is meat, fish, eggs, cheese, salad veggies greens cooked as simply as possible, so you can see the ingredients is best.
Remember you can ask what's in foods.
I'd been warnedd by friens who'd cruised before that I'd gain weight. I didn't, I LOST. I also didn't use the lift.
My BG stayed in my target zone the whole trip
Have a great holiday
Hana