Why do Dolphins and Whales sleep with one eye open?

<p>Do fish sleep?&nbsp;How can sea&nbsp;creatures sleep if they have no eyelids?&nbsp;How do marine mammals breathe while they sleep? For free home activities sign-up at <a href="http://www.WhoSmarted.com" rel="noopener noreferrer" target="_blank">www.WhoSmarted.com</a></p><p>See Privacy Policy at <a href="https://art19.com/privacy" rel="noopener noreferrer" target="_blank">https://art19.com/privacy</a> and California Privacy Notice at <a href="https://art19.com/privacy#do-not-sell-my-info" rel="noopener noreferrer" target="_blank">https://art19.com/privacy#do-not-sell-my-info</a>.</p>