Microman wrote:
Google hangouts, similar to Viber?
Yes and no. You need to install both Google Hangouts AND Google Voice and set them up. Then you can make free calls to U.S. and Canadian numbers using Google Hangouts or Google Voice. (Don't know why both are required.) You can also use it to make paid calls to other countries. You'd have to check rates.
Our T-Mobile plan has $0.20/min for voice calls when abroad, in most countries. This applies for both making and receiving calls. We leave our phones in regular mode - Airplane mode kills the free data access you get from overseas roaming with T-Mobile. If someone calls, we either ignore it, or answer and then call them back via another method (FaceTime, Google Voice, Viber, etc.)
The $0.20/min also applies to making calls to numbers in the country we are visiting. For simplicity, we sometimes use this for things like making a dinner reservation.
I'm sure all the places you will visit will be within the T-Mobile international roaming plan. The only place we've been which was not covered was the Maldives.
If you want to put the phone in WiFi-only mode when on the boat, you should still get calls on T-Mobile WiFi calling (assuming your phones support that). And, unlike AT&T, T-Mobile does not charge the $0.20/min for WiFi based calls. They are included in your plan regardless of where you are in the world.
But be careful: if you make a call to a number in Germany, say, while on WiFi calling, T-Mobile might treat it as if you called Germany from the U.S. ($3/min?) instead of giving you the $0.20/min international roaming rate for calls. I'd check on this with T-Mobile before you go. But T-Mobile WiFi calls to and from the U.S. are just the same as if you called them from home. You can disable WiFi calling if you need to (just turn off WiFi), but you need to remember to do so.
Good luck.
- Winston