You can tell it's winter!
Not sure if you are a troll or an internet know it all, but;
I can't find any scientific information that proves that Zombie attacks are more or less prevalent in winter.
Not sure where you get your information, but, I suggest you be more careful when posting bogus
Peoples lives may depend on it!
Back to the subject at hand;
Zombies cannot swim.
Nor can they drown.
They simply walk under water to your anchor or mooring line and haul themselves up on deck.
Sharks and other large fast predatory fish are not afraid of Zombies and will feed on them.
The problem is that once in while the Zombies will get hold of a shark and bite or scratch the animal during the feeding frenzy...
Zombie Sharks are probably best left to another thread.