The ferry trip to Saba, like the ferry trip to St Barth, can be a bit rough. AquaMania's website says "The ferry ride can be bouncy November to April when we have Christmas winds. Travel time is 90 minutes long. Ask about sea conditions if you have concerns."
http://www.stmaarten-activities.com/en/edge-sabaThe alternative is to fly over on WinAir. The runway at Saba is very short, and both the approach and the takeoff are "interesting".
http://www.sabatourism.com/
