If you want to get the Pearl Capture Stamp you just need to go to the Ice Berg and then play aqua grabber and choose clam waters and then the first one. So once you're there just watch the video below for a simple guide on how to get the Pearl Capture Stamp. I tell you where all the little pearls are also. So Good Luck getting the stamp and I hope this video helps!
I realized I also got the clam treasure stamp! You can get it to by getting the secret treasure as shown in the video! Good Luck!