I really don’t like the “Ruined market plus Lost City” analogy at all. While all of these card effect analogies are really stupid, at least call it like, a Market Square, instead of something that weirdly implies that Seaway helps you cycle or gives actions or something.
Seaway helps you cycle exactly as much as getting a lost city and ruined market together does, which is to say not at all (bar from the card you gain with it, which was also included in my comparison).
I know it's odd, but my point was to compare seaway and ruined market, and the difference between them is lost city and whatever card you gain with the seaway.
I agree that a simpler way to explain seaway is as giving you a free market square sans reaction with your chosen card, but a market square sans reaction is the same as a lost city and a ruined market that always turn up together, and the latter explanation allows for the direct comparison with ruined market.
Obviously tons of things change these equivalences, like TfB and things like vagrant or WoW that care about types and cost for draw, and pileout considerations are different etc etc, but I think people understand that what's being considered is the on-play action effects of the cards for your hand and action/coin/buy pools, for which, for instance, SeawayedPoacher = Poacher + Market Square = Lost City + Ruined Market + Poacher