This is a nudge nudge wink prompt, huh? Is the association perchaps with the moon as raccoon mentioned? Saying other ones in that context makes it sound like a celestial body. His relations to Poseidon by extension links him to the sea and fishing (not to mention his history)-- which makes the moon among the choices the best fit. The moon affects the tides after all, which also affects fishing to some degree.
Looking into it now, Oscar has more incriminating ties to Poseidon than what I've seen in the threads so far. First, storms are Poseidon's domain, which is coincidentally also Oscar's self-made nickname. It's also noted that white and black bulls are sacrificed to him. Poseidon is of course linked to seas and fishing, which are highly involved in Oscar's lineage/ancestry. The family on his mother's side were fishermen and lived near the coast, after all.