"E" for effort

Seen at the Shimoda Floating Aquarium:

You can just imagine the story behind this sign:

"Bad news, Tanaka-kun. It turns out there's supposed to be an "e" at the end of "Marin".

"You've got to be kidding. The damn thing's already finished. What the heck am I supposed to do about it now?"

"I don't know, but the boss says to get an "e" in there or you're fired."