This is just my interpretation so here goes:
"Punk" as a suffix is inherently about anti-establishment. Therefore:
Cyberpunk -> Mega-corporations control the media and hoard resources and anyone not consuming mindlessly is a threat
Desertpunk -> Water is hoarded by either petty warlords or mega-corporations and the hero is often someone fighting or existing outside the system. Mad Max comes to mind but Tank Girl also. Basically, any setting where drinking water is treated as crude oil and all the conflict that entails.
Oceanpunk -> Not quite the opposite of Desertpunk. Instead of arid deserts, it's vast swathes of ocean with little islands (floating or stationary). An authoritarian regime controls or wishes to control the waters and its inhabitants. Land can be a resource or ancient technology from the "old world" can drive the conflict. One Piece, Waterworld, Flapjack, any setting where boats are used frequently as transportation and the setting. I wanna see more submarines in this genre.
Scavengepunk -> The oil's been used up and global war has rendered progress & production stagnant. People scavenge junk to meet their needs but this junk is very much a finite resource. The regime either hoards what they scavenge or forbid the scavenging of certain goods, fearing it could upset the power balance. People who can actually manufacture or invent new tech might be persecuted cuz being able to build your own stuff instead of scavenging just disrupts the status quo. These types of stories usually have 1 of 2 MacGuffins: the main hero restarts some dangerous old-world tech or invents something powerful. Mortal Engines is technically scavengepunk and steampunk combined.