i wonder what they look for

A mystery for the ages, I dare say.

She should join them~ ;3

She did, out of curiosity. She's not convinced it was worth it.

Oh really? How so? XD

Duck penises are generally quite long in relation to body size as well as corkscrewed. Ducks are generally promiscuous and the drakes can be very enthusiastic when in the mood. Plus, in order to prevents previous rivals from successfully fertilizing the female, the drake is basically reaming out the female. In response, female ducks' cloacal structures are twisty with a number of pockets and dead ends to make insemination much harder. Duck sex is essentially nonconcensual when looked at in human terms. I imagine having a drake force himself into a mammalian vagina would not feel very good to the mammal.

As for Cynthia, she was curious and maybe teased them a bit, but didn't think much about it. Then, when she bent over and looked under something without thinking about it, a drake nipped at her bikini bottom and actually managed to partly pull it off, certainly enough to reveal a bit more than she intended. It took her a moment for this to register, but this was enough of a delay for another drake to pounce.

Ouch.

Cynthia discovered the peculiarities of drake anatomy firsthand, not once, not twice, but thrice (one for each duck). The first shocked her. The second made her realize a duck was doing her so what should she do? What to do? The third got away with it as she tried to get to a point where she could stand up and shoo them away and get her bikini back in place. All the while, she let off a string of profanitype and grawlixes. And all she wanted to do was get out into the sun and water.

It's probably less a pornographic scenario than an uncensored America's Funniest Videos type of situation.

Ah, I see.
Too bad I wasn't there to see her butt sticking out of the water with the ducks. XD