Nope it needs a living host to spread
If the fish eat something that contains it then...
No I dont think so, bubonic plague is spread thru fleas and spread thru the help of rodents and mammals.
You gotta also think of it like this. The sea is a wast body of water and even if you were to pour something bad into it. The amount a ship like this with its bodies would harm it are very small. Because even if it could spread through water, it would get dilluted to such an estimate that it would pose no harm. Also the fleas and bacteria and rodents would die out in the water.
T-the epidemic isn't going to spread throughout the sea, is it?