Where does the wastewater go? (Shabbos 100b)

The gemara on the bottom of 100b says that according to Rav Chisda and Rabbah who require a four by four area how can you the wastewater outside the ship? The gemara says that maybe they just put it in the same four by four area where they get the water from. The gemara rejects that because that would be disgusting. So the gemara ultimately answers that a four by four area isn't needed to dump the water and you can dump it down the side.

We were bothered by two points on this gemara. First of all, why is it disgusting to draw water from there, you're just making four walls but all the ocean water is still mixing? Also, why can't they just make another four by four area for dumping the water?

The Pnei Yehoshua answers that the problem isn't that it's literally disgusting. Of course, it doesn't matter where you pour the water but that people will just be disgusted at the idea of having a designated area set aside for the wastewater. Therefore the Chachamim didn't require you to do this.

This explanation doesn't fit into Rashi (the P"Y admits this) and there are other explanations found in the Ritva and other places but I liked this one the best