Like most Korean festivals it goes by a few different English names, and is often called the Jindo "Moses Miracle." I loved the comment I got from a reader years ago: "The tide went out! It's a miracle!"
If you don't get around to visiting the island this year I'm sure you won't take the regret to your grave. But if you're in Korea, make the effort to visit some place rural (I'm not talking Gyeonggi-do) like Jindo or one of the other counties in Jeollanam-do (or in other provinces, too). Rural Korea isn't "backwater" or foreigner-unfriendly like a lot of Dave's ESL Cafe users will have you believe, but it will show you a side of South Korea worth seeing.