If you have an annual subscription, you can be without internet access for 99 days.
I would think that just being online with the cc desktop app running the day before you leave would be sufficient to get 99 days.
But this is just a guess - someone correct me if I'm wrong.
I'm also guessing that you possibly will find open WiFi networks when the ship is in a port.
I don't use LR Mobile, so I'm afraid I can't help you with that.
If you're referring to the 99 days, I found this
For annual members, you can use the apps for up to 99 days in offline mode. Month-to-month members can use the software for up to 30 days in offline mode.
Hmmm... looks like my previous post never posted. I will try again....
Thanks for the replies everyone. I am on annual membership so 99 days should mean I will be ok. Any thoughts on using LR Mobile without internet access. I have two periods of 5 days without landfall and could really do with some way of transferring images from LR to LR Mobile during that time.
No internet means you can't use the features of Lightroom Mobile.