According to the press release sent to Moon Phase, the new anime will air in the summer and follow two sisters, Marin and Urin, who live in the sea and yearn to try out the surface. (Part of your wooooorld...oh, wait.) One day a pretty ring stumbles into their watery home and they decide to scoot up to the land to try and return it, opening up an unexpected magical can of worms when they meet with a high school girl named Kanon.
Oh, and if you were curious as to what is this illustrious new anime based on? A pachinko game! The press release claims it's Japan's most popular.