Giddy and Sheila's fathers were both killed by sharks. When Estella finds out about Sheila's...
Estella: I had no idea sharks were so....
Sheila also mentions that they only ever found a limb of her father and that's what was buried. When Pru talks about her dead father, Estella assumes it was a shark as well. It was a boating accident this time but Pru also mentions that she only ever found a limb of hers too. Estella accidentally bursts out laughing when she hears this.
At the end, Estella starts pleasuring her husband on a train. He's clearly enjoying it but the things he's saying.
"Stop, we'll be arrested...(she keeps going)...we'll be excommunicated"