Ferry from St Lucia to Martinique
 

Dreaming of another trip to the Caribbean - hoping to combine it with carnival in Martinique by flying into and out of St Lucia and splitting time between the two islands. I once took a very sickening rough ferry ride off Cancun to Isla Mujeres on a clear February day that didn't even seem particularly windy. That ride is still in my mind two years later, and I'm wondering what the trip is like between St Lucia and Martinique. Not surprisingly to anyone who has read this far is the fact that I am also not a fan of small aircraft. So what do you think - what have you experienced or heard about this particular route? does my plan sound like a one that will result in seasickness or not?

I'm also interested in this question - as someone who is hoping to get to Martinique (& looking for inexpensive options...) - and who also got very very ill on that same ferry ride from Cancun to Isla Mujeres.
FYI - what I can add is that 2 yrs ago we took the ferry from Dominica to Guadeloupe and it was very calm and I had no sea sickness.

I've never take this ferry, but it's a very long ride (probably 3 or 4 hours) over open ocean. However, it's the same ferry line that travels from Dominica to Guadeloupe, so perhaps the ride isn't so bad.

I've done a long ferry ride (Mykonos to Santorini) on a fast catamaran-ferry, and while it was a little rough coming into and out of port, I didn't really have any problems at all. But I've never done anything comparable in the Caribbean ... just short ferries to Anguilla, St. John, etc.