I try not to be too much of a food snob but there are a few things that just sort of make me nervous for no good reason, and having sushi far from the open sea is one of them. This is bogus for any number of reasons, most notably that a great deal of all restaurant sushi even in Japan is frozen at some point - either at sea, right on the fishing boat, or later on for the purpose of shipping or killing parasites. (If you need a citation on that, check the NYT, and especially note the quick list at the end of what's usually frozen and what's usually fresh.) Nonetheless I maintain a Spurious Sushi Exclusion Zone of about 100 miles beyond which distance from open water I am loath to order sushi.
Naturally, once you've created an admittedly pointless geographic entity, at least if you're me, the next step would be to map it. Sure, it's usually pretty easy to know if you're near the ocean or not, and pretty easy to measure on a map to any given place. But where can I get a map of everyplace that's more than 100 miles from the ocean? Sadly, I came up empty, but along the way, I noted this map of the coastline as altered by rising sea levels of various magnitudes. Limeduck world HQ seems safe to +13 meters, more if I'm willing to commute by canoe directly from the window.
Naturally, this level of flooding would only push the SSEZ deeper inland.
Another note on this topic is that by my rule, there is nowhere in all of Japan where I would not order sushi, because in Japan the farthest from the sea you can get is only 120km (~75mi), in Maebashi. This leads me to consider reducing the SSEZ to 120 km. Because I need the greatest precision in my bogus heuristics.