I was studying the Volendam deck plans and found there to be ample viewing space up on the top provided we find a calm spot and can aim the ship in a direction along a line between the NNW and SSE directions. As normal, somewhere near the center of the ship will provide the smoothest location but NO WHERE is trouble free for photographers.
Using hand held binoculars and a VERY PORTABLE point and shoot camera I am not concerned about viewing the eclipse as much as what else can be imaged the same time. Hopefully we will not be dodging clouds, turning the ship just as totality starts, and moving at speed (causes a significant wind change across the deck sometimes). When repositioning, it is important to be mobile and at the same time sympathetic to those with loads of equipment. The best thing to do is tell them "Forget that stuff, watch the eclipse instead!".
Here is the link for the Holland America cruise ship Volendam deck plans. It will start with the lower deck, use the pull down menu to select the ship Volendam, then the upper decks.
There is one deck of particular interest for photography. It is called the Oasis and appears to have palm trees. That is awesome foreground material and requires further investigation. Unless the decor is changed before the eclipse, this location will be a great photo place. Even so, it is high up and should present the least problems if the ship needs to reposition to avoid some clouds. It will most likely be reserved by some group already.
I should mention that there will be several different eclipse groups with their own programs on board at the same time. It is going to be a lot of fun as many of the experts are eclipse chasing friends and associates. We are already planning to meet up on board. We already have our own small group of eclipse chasers. More on that later except to say that one of them will be passing the ONE hour mark of totality on board. This is not something that is easy to accomplish. Check out the web site to see what I mean, there are less than ten people listed who can claim that mark. Eclipse chasers listed by total time.