Because of that, she was a little worried about Sunday’s Marnie-centric episode. "

she tells EW.

“That included speaking differently and having a different attitude and tattoos and all that stuff.”

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Credit: Mark Schafer/HBO

Williams tried to keep Marnie out of it too, in a way.

They end up kissing and falling into the water, where Marnie lingers.

“I had no idea how hard it is to act underwater,” Williams says.

“And it’s very hard to breathe so that you don’t have bubble boogers.

That proved to be difficult to juggle with acting out the emotions she wanted to depict.

“And that’s a lot to do with your face in a couple seconds.”

“It’s pretty clear that she’sjusttold everyone about the divorce,” she says.

“The Charlie thing she keeps to herself. "

See what that means for Marnie when new episodes ofGirlsair Sundays at 10 p.m.