So I am making a campaign where the tarasque is on a rampage and the players have to ask a deity to help them defeat it. So I was thinking of making them go to the different planes where they could find a deity like the Astral sea, but I have no idea how it looks like. Does it look like a big ocean where you can find some islands with gods or is the sea term just to represent an imagery like the Milky Way looks like milk? If you can help me with which plane to go that would be nice. Thanks.

I am making a campaign where a tarrasque is on a rampage, and the players have to ask a deity to help them defeat it. I was thinking of making them go to the different planes where they could find a deity, like the Astral Sea, but I have no idea how it looks. 

Does it look like a big ocean where you can find some islands with gods, or is the sea term just to represent an imagery like the Milky Way looks like milk?