Sharks Cannot Smell a Drop of Blood From Miles Away
Although it's not advised to be in shark-infested waters while bleeding, it's not an immediate death sentence. Sharks do have enhanced odor receptors that can sense as little as one part blood to 10,000,000,000 parts water. But, the ocean is much, much bigger than that and it takes a long time for blood molecules to drift far enough in high enough concentration for sharks to react to it.
Bats Aren't Blind
The term "blind as a bat" doesn't really make much sense if you think about it. All bats have functional eyes. Despite the fact that most bats live in darkness and use echolocation to guide their way, every single bat can see.
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