Mysterious ruins in the ocean

[Dedrytus]

Hello,
I found something funny in the water and I wonder what it is. It has no tooltip, it is not visible in the strategic view. But it is "real", has reflection in the water... and looks nice. Do you have an idea what it is? [new frontier pass, no mods]

 

[JJOne]

A bug.

 

[Uberfrog]

Bridge graphics have been showing up in the sea for some reason.

Takes me back to the Seahenge days in Civ V.

 

[AvianBritish]

Reminds me of these 'mysterious ruins' I found at sea a within the last 4 years:

Spoiler The Pink Cloud Invasion :

Spoiler The Great Cardboard-Cut-Out :

 

[AntSou]

Reminds me of these 'mysterious ruins' I found at sea a within the last 4 yea

That pink looks oddly appealing.