Hailey Bieber, More Hot Celebrities Cool Off With Cold Plunges

Even the hottest celebrities need to cool off every so often ... sizzling in the bathtub after taking cold plunges -- and, we've got all the pics for you to dive into.

Hailey Bieber leads the parade of celebrities jumping into the icy water -- floating in a small bathtub just like racecar driver Lewis Hamilton, who looks like he was trying hard to breathe through his discomfort.

Nicole Scherzinger and Zedd gave fans a full look at their bodies ... each drawing eyes to their impressive chests.

Soccer star Cristiano Ronaldo decided to take part in a real polar bear plunge ... walking down the steps and floating in a freezing pool -- while outside in the middle of winter.

Actress Kate Hudson brought pal Angi Fletcher to bath time ... hopping into the same tiny plunge tub. Both couldn't help but bust up laughing while trying to sink beneath the icy surface.

And, Billie Eilish's big brother Finneas gave fans a look at what it's like when a celeb is done with their plunge ... hopping up out of the water, chest and legs wet with his hair tousled.