Causalities at sea rarely occur these days, but they do happen from time to time. Since I've been in, the Navy has been always forthcoming on reporting such incidents to the media.
While at sea, Navy Personnel are relatively safe. But during certain evolutions such as Boardings and RAS's (Replenishment at Sea), there exists a high potential for incidents as the danger level is high. This is why we train and repeat these evolutions quite often to ensure that everyone knows their job.
If you train enough, it becomes instinctive.