This question: [Can you get enough water by eating only fish?](https://biology.stackexchange.com/questions/21827/can-you-get-enough-water-by-eating-only-fish) asks if a person could survive on fish alone. **Can a person survive on fish and/ or blood alone of any species if stuck at sea or animal blood as a last resort where there is no water or fire?** 

Obviously if it was a fresh water fish there is water, but there are fresh water mud skippers that can breathe air and the water to tainted to drink in that case a fresh water fish blood maybe safer than the water. <https://chemistry.stackexchange.com/questions/115901/what-can-i-eat-that-will-help-metabolize-blood>

Desalination would be the best way to process the blood but this is in emergency situation scenario.

From @PTwr Comment's Link: *If you drink blood regularly, over a long period of time the buildup of iron in your system can cause iron overload. This syndrome, which sometimes affects people who have repeated blood transfusions, is one of the few conditions for which the correct treatment is bloodletting.* <https://what-if.xkcd.com/98/>