Oceanside settlement is located close to the ocean and the beach but when it comes to scale and prep the fish they use carp (latin: cyprinus carpio) which is known to live only in freshwaters - lakes and rivers far from the sea.
At the beginning of the episode the walkers don't behave according to established walker behavior. Walkers are said to 'hunt' mostly by smell, yet the walkers released from the beached ship totally ignore Ezekiel and Jerry (next to the door) and immediately walk towards the army waiting for them (many meters/yards away). It could be argued that the Walkers were attracted to the army by sight or sound, but this wouldn't hold up because they weren't making much sound and most of them were hidden behind shields.