Does it extend down low enough to impact on the sailing fraternity? Do they have an equivalent notification system, NOSEMs?
There are the equivalent of danger areas in the sailing world too. Typically marked on the charts as exclusion areas such as firing ranges, naval facilities etc. You can phone ahead to see if the areas are active before you set off. For example,
the Lulworth range on the Dorset coast
Often these are patrolled by fast powerboats that will come and encourage you to leave if you have inadvertently strayed in - similar to being intercepted by fighter aircraft.
I'm not aware of any equivalent electronic notification or website that lists/promulgates the information in the same way as for pilots. Perhaps because it doesn't tend to change that often.
There are also more temporary/informal arrangements. For example, at Devonport, I have had the pleasure of being "encouraged" to leave the main channel while a warship came in to dock. The gentleman with the machine gun on the rib speedboat was very clear and professional about his instructions, but there was no question about whether I would comply or not!