Note #1: This level is first available after the "Swimming with Stars" level if and only if you have at least 90 Electoons (which means you must have successfully collected the almost all [≈91%] of the Electoons up to that point).
Note #2: Many players have suffered glitches while trying to complete this level. For suggestions on what you can try to remedy the situation, read the comments here.
In this video, I show you how to obtain the Skull Tooth for the "Pirate's Treasure!" Tricky Treasure level of "The Sea of Serendipity".
Finally, a Tricky Treasure level that's actually hard! It's not too bad once you get the pattern down, but it's not going to go easy on you while you're learning.