I have no idea about flooding in this area........although I don't recall EVER hearing about any serious flooding, so I suspect it's not a really major issue (woulda heard something, sometime, right?)
As for WiFi and your Verizon 3G phone - - there is free WiFi on the ship, but I'm told it doesn't reach the cabins. You can use an iPad or a WiFi-enabled laptop in a lot of the common areas, including the lounges and the library. However, while at the hotel in Prague, I've been told the WiFi is spotty, and expensive. You might try going on the Don Giovanni Hotel website for their email address, and ask them directly what the costs are.
You ABSOLUTELY should be calling Verizon to get definitive information about "roaming charges" while in the three countries we'll be visiting. Calculating it by way of guesswork or by what others "think" the costs is not the way to go. These "roaming charges" get really expensive, really quickly, and you should know for sure what your carrier costs are. Get that info directly from them.
As for what I'VE decided to do? I'm leaving my laptop home, but I'm carrying my iPad (it travels well.) And I'm with T-Mobile for my cell service, and it is NOT cheap (particularly in Prague!!) I plan to carry the phone, but simply leave it OFF unless I absolutely MUST make a call.
See you onboard!!
Ken Allen Moore