But from her teasing grin and relaxed pose you would never have known how cold the tub was.
She shrugged off the icy exchange with a flick of her head and a view of her bottom as she turned and stooped to conquer the water.
Apollonia posted: "@lumi.therapy X @nipcharity today i started my 10 day challenge in my lumi ice bath, for an amazing charity who provide realistic 3D nipple tattoos for people post mastectomy!
"I feel grateful to share this with you all on world cancer day #lumicoldclub."
Fans called her "perfect" and "sexy" as she launched her glacial but glowing session of bathing.
The nip charity - aka the Nipple Innovation Project" - aims to "empower cancer survivors" by helping them find specialist tattoo artists and fundraising for the inking itself.
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