Tens of thousands of ferry crossings take place every single day all over the world. And yet some people still wonder whether travelling by ferry is safe.
Cross channel ferries and other ferries in Europe and America are extremely safe indeed. The number of accidents is far less than almost any other form of transport whilst the chances of being bothered by outsiders are pretty much nil.
Ferries are one of the easiest and cheapest ways to go; just consider how long it now takes to merely go through security at an airport. Then of course there is the fact that the cost of cross channel ferries can be shared by everyone in the car, rather than being a fee per person.
Therefore, unless you are considering boarding a ship in Somalia or Bangladesh, you are likely to be extremely safe, and even those worried about sea sickness or any other problems that may be exacerbated by turbulent seas are likely to find many forms of medication which make it extremely easy, and a transportation type that is far more relaxing than any other.