For open sea waves the National Weather Service provides wave height forecasts over most of the waters where cruise ships frequent around North America. Go to the link below and click on the top left and change "hazards" to "wave height". You can use the slider bar at the top to change the forecast time. Beware the website is a little slow to load and render but the data is pretty good.

https://digital.weather.gov/?zoom=3&...rue&barbs=true