Plural or Possessive

Is it plural? Or is it possessive? My students have a hard time deciphering between the two. Once I introduce possessive nouns in first grade, I find that many of them add an apostrophe to just about any word that ends with an s. This is one of those skills that first and second graders, and probably third graders, too, simply cannot practice enough. I created an ocean themed game that will surely help my students, and, hopefully, yours, strengthen this skill. It comes with a game board, 24 question cards, and an answer key. Here's a little preview:

 If you purchase this game, and you like it, please leave me some feedback. I ALWAYS enjoy reading the sweet comments that you all write. Thank you!