Lois just barely restrained herself from cursing in surprise (she knew Clark didn't really appreciate her occasional slip into language, especially not around little Conner), and her eyes narrowed.

"Oh, really?" she half-snarled playfully. Going for Conner would not be strategically helpful here--Clark could just get her from behind.

So, in an attempt to escape this before getting captured, Lois dove under the water herself, hoping to at least knock Clark's legs out from under him and distract him long enough to get away.