There is one late-game shell in Another Crab's Treasure that is extremely difficult to obtain: the Helmet of a Certain Hero, which is located in one of the final areas of the game. If you want to complete your collection of all 69 shells, you will need to select this one as well.
Another Crab's Treasure: A Certain Hero's Helmet trophy guide
The Helmet of a Certain Hero is part of obtaining two specific achievements in Another Crab's Treasure: Shellslike and Shell Seeker. If you want to collect both of these trophies, you will need to find your way to the Old Oceanwhich is one of the very last parts of the game.
While in the Whitewashed City, look for the elevator. Head upstairs and look for a room with two crabs with Snowball shells. Go left, then climb up the pile of rubble and go through the crack in the wall. It will be a jumping puzzle that I found incredibly difficult to complete. It's a lot of precision platforming, so I'd go into the Accessibility Menu and turn off fall damage to help you through this. If you die, it's very annoying to come back, so that setting really saved my tail.
Related: Best Shells in Another Crab's Treasure
Also, whenever I found myself on solid ground, I saved my game. That way if I failed and got stuck somewhere where I couldn't complete the puzzle, I could force close the game and try again.
At the part where you have to jump on bubbles to get past some urchins, I damage boosted through it instead of doing the puzzle as intended because it was so challenging and frustrating. If you have a lot of trouble with this section, don't be afraid to use the Help menu to help you.
For more Another Crab's Treasure, check out How to shoot a crab with a gun in Another Crab's Treasure on Pro Game Guides.
