While @alyssamma is correct, the reality is most phone users do not have wifi calling turned on. So SMS Text messaging will not work in that case.
If you need to send SMS Text you must enable wifi calling on your phone before you leave on your cruise, and verify it works. You cannot turn it on once you leave your home service area. Sometimes you need help from your carrier to get it working. Test it by going into airplane mode, enabling Wifi and connecting, then see if you can make a phone call and send SMS text message.
If you use Facebook messenger, or you all have Apple products and user imessage, or you use Whatsapp, etc. you can just rely on Wifi and don't need to enable Wifi Calling.
Also, be aware: SMS Texting is notorious for delivery issues, especially when relayed through WiFi calling. If you don't get a reply in an expected timeframe, send it again.