Would ocean water cause our cells to swell with more or to shrivel ?

 The cell shrinks

Explanation:   Seawater is hypertonic. If you place an animal or a plant cell in a hypertonic solution, the cell shrinks, because it loses water ( water moves from a higher concentration inside the cell to a lower concentration outside ). So if you get thirsty at the beach drinking seawater makes you even more dehydrated.