...and all the way up, if you consider Earth as an island in the lake of the solar system, which is of course an island in the galaxy, which is an island in the local group, etc.
I mean, "if" is doing a lot of work there! Earth is not an island because it's not surrounded by water. Poetically, sure, it's a nice metaphor, but it's only a metaphor.
https://www.youtube.com/watch?v=M186s319ob8&list=PLa0TgREKn1...
Similarly, my home is not an island even though the air around it contains water vapor. Nor is my home an island because there are some puddles on the street outside.