It would cause nothing but local effects, and unless slowly leaking, not for long. Think about the billions of gallons of nasty stuff that has already been dumped in the oceans as far as chemical. Bio, unless fish can catch Smallpox and Ebola then give it to me when I eat them, no problem. And I think there are already multiple nukes that are down there now.
If it can be captured without too much risk to our guys, go for it, or sink them.
(Besides, I'd like to catch a two-headed fish with only three legs ;-)
Yum. Tomorrow's entree: Lightly breaded fish legs, served with a caper dill butter sauce over a bed of lemon risotto.
You catch em, I'll cook em!