After you do the quest for RDC in Cignath Mór the coral in Sayuka will be removed. But I noticed that it still casts a shadow on the sea, like seen on the screenshot below:

 

Hello handsomenat,

 

I love bugs like these. Thanks for bringing it to our attention! Ill have QA get this in if it is not already

 

best,

 

-Caleb

It's hard to see in the above screenshot, but theres bits of shadow left over from the coral near the bottom of the screen, more easily seen in this screenshot: https://steamuserimages-a.akamaihd.net/ugc/954083064338678837/8C741C2E2215FBC86A07ECE22C94BDE22D7DE4C1/