Nagas are serpent deities in Buddhism, and it's pretty obvious why this mandala is named "Naga of the Seas". It's reminiscent of the ocean and octopii, even though Nagas are actually more like snakes. We have version of [Naga of the Seas in color](/b/naga-of-the-seas) if you want some inspiration.
The word "gati" refers to one of four "destinies", or realms of existence: human beings, heavenly beings, tiryancha (animal) beings, and infernal beings. It is believed that your current life will shape your destiny for the next life. There's an image of [Path to Gati colored with pencils](/b/path-to-gati) on the blog.