More Fish in the Sea

There are plenty more fish in the sea is the last thing you should say to a necrophiliac.

Necrophiliac
Fish
Necrophilia
Sea
Death
Short jokes

Explanation

This joke plays on the idea that a necrophiliac is interested in dead bodies, not live people. So, saying "there are plenty more fish in the sea" which typically suggests there are other living potential partners, would be wildly inappropriate because it is very different from what they desire.