xxsim a cheaper tariff on water, and this I found to teltarif.de
Test: Roaming-Karte xxSIM mit kostenloser Erreichbarkeit - teltarif.de News
>>>>...For cruise passengers make installed on cruise ships mobile systems a particularly drastic cost dar. Again XXSIM offers on some ships that are primarily in the area of the Baltic Sea probably go, interesting prices: Incoming calls cost 30 cents, outgoing 71 cents per minute or part thereof. Other providers may charge more here than tenfold.<<<<
My favorite sim and VoIP for roaming in Europe and worldwide:
UWT-mobile and Xxsim: for call+sms in Europa extern and Worldwide
ToggleMobile: for internet+call+sms only in EU intern
(VoIP/Sip) FriendCaller or SipCall.ch: Worldwide sms+call