I've had this happen several different times. I can see an item, but I can't physically get to it. Once a building blocked off a whole half of the island, and I could see an item on the other side of it, but I couldn't get around the building. Another time, a rock was in the way of my reaching a shell in the water. This time I decided to take a screen shot.

There is no way that I see to get to the cuttlefish. If you go to the other side of the building, it opens the Hero requirement popup, and you can't get closer.

I wasn't really planning to say anything about it. I thought it might just be me, and maybe still is, but since it has happened more than once, I decided to post this.

This has been reported a number of times, unfortunately because of the way the islands are generated, it is impossible to avoid this completely, so it's something you just have to live with happening from time to time

Oh, well sorry then...