Do horses get sea sick?

Siberian ponies on the Terra Nova ship
during voyage to the South Pole

Yes, horses get sea sick.  Because they can't throw up, they colic instead.  Per Live Science"

"When Earnest Shackleton trekked to the Antarctic, he brought ponies (and whiskey) with him to help. According to his journals, those ponies didn’t fare so well on the water. They, like many people, responded to the pitching seas with confusion and dizziness. But because horses cannot vomit — the sphincter that goes from their esophagus to their stomachs is too tight — they experience colic instead. But even though they didn’t lose their lunches, the ponies were definitely seasick."





After the original hay ran out, Shackleton fed the horses a meat based diet.  “It consisted of dried beef, carrots, milk, currants and sugar, and was chosen because it provides a large amount of nourishment with comparatively little weight.”  Several of the early Arctic and Antarctic explorations fed meat to their ponies.

Although the ponies survived the sea voyage, none of them survived the unsuccessful trek to the South Pole

For more information, you can read the article at the link below:
https://www.livescience.com/33771-animals-seasick.html