It should always be remembered that Batteries not only be covered (at least the terminals) but also secured to prevent movement. Yes boats bounce and rock. Ever seen a galley cleared out before? I have in Hells gate NY once. Now look at tue two pictures and see what the possibilities could be? I walked into this today on a modern SeaRay.
The hull is thin enough the fire will almost be self extinguishing.
A marine surveyor will always catch this and say, “ABYC E-11 requires any continuously energized part to be physically protected with boots, an enclosure or some other cover. These are usually at the batteries and the connections in the starting circuit. Whether it's a positive battery terminal or the positive starter post, if it's not protected by overcurrent protection (breaker or fuse), then it needs a boot or enclosure.”
Imagine dropping a wrench on that!