If you lose your last hit point by falling into water, Bubsy will literally drown. This is accompanied by a line where he says "drowning in responsibilities... and water."

You can fully submerge in some levels, meaning you can theoretically drown, but there's no air meter, so no literal drowning.

You cannot drown in Inverse Ninjas Vs. The Public Domain.

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.