There is a scene where a character is dropped into water, but at this time it is undetermined if you can drown in hypothetically or literally.

You cannot go into any body of water without mods, so you cannot hypothetically or literally drown.

You cannot drown, hypothetically or literally.

You can hypothetically drown in chapters containing diveable water (i.e. the Cosmic Realm chapters).

There are rivers of... something in the main area of Episode 1. Jumping into them makes you respawn, so if you want to count it as water, I guess you could literally drown?

You, the player, cannot physically enter this water to drown. Your fish, being fish, cannot drown.

You can literally drown in areas containing swimable water.

There is water in the game, and you can fully submerge. However, when playing as Annie, she has a fish bowl on her head, implying that she can breathe. (Unlike Anton, who just has a pair of goggles.)

If you fall into lakes of goo, you take damage and respawn. So you can literally drown in this game. About a sea creature. Who spends all his time underwater. And breathes water. I'm going crazy.

There's a fish tank in the boss' office, and jumping into it kills you instantly with a unique sound effect playing. Therefore, you can literally drown in Orbo's Odyssey.