"Ocean Siren" - Sensory Sculpture by Jason deCaires Taylor

This is not meant to warn ships away from the Great Barrier Reef in Queensland, Australia, as its size and location prohibit that function. It's main function is a sensor for water temperatures in the area. The colors of the various LED's within indicate ocean temperatures, and are a beautiful way of indicating important ecological metrics, especially in relation to the coral reef it protects.

https://www.underwatersculpture.com/projects/ocean-siren/