There is one late-game shell in Another Crab's Treasure that is extremely difficult to obtain: the Certain Hero's Helmet, which is located in one of the final areas of the game. If you want to complete your collection of all 69 shells, you'll need to pick this one up as well.
Another Crab Treasure | How to Find a Knight's Helmet | Shellslike Achievement/Trophy Guide
The Certain Hero's Helmet is part of completing two specific achievements in Another Crab's Treasure: Shellslike and Shell Seeker. If you want to collect both trophies, you'll need to make your way to the Old Ocean, one of the very last parts of the game.
In Bleached City, find the elevator. Go up and look for a room with two crabs with Snow Globe shells. Go left, then go up to the pile of trash and go through the crack in the wall. There will be a jumping puzzle that I found incredibly challenging to complete. It’s a lot of precision platforming, so I would go into the accessibility menu and turn off fall damage to help you get through this. If you die, it’s super annoying to come back, so that setting really saved me.
Related: Best Shells in Another Crab's Treasure
