MAP32: Caribbean is the second secret map of TNT: Evilution and can be accessed from MAP31. It was designed by Dario Casali and uses the music track "Into Sandy's City" from Doom II.
Inside the central building of the first area, there is a large square room with a vaguely sun-shaped skylight. Surrounding this room is a narrower hallway. At the west end of the hallway is a wooden wall with a pair of vertical designs carved into it. Open the wall between the designs to reveal a small secret alcove.
After getting the yellow skull key in the "sewer" area inside the main building, return to the room where you found the blue skull key. A large area to the east has opened up, letting you get a combat armor vest. Picking up the armor causes another nearby room to open, this one containing a switch. Flip the switch, then return outside. Head to the area north of the central building. There are two small "shacks" in the far east and west ends of the water. The eastern one requires the blue skull key to open, but the western one was opened by the switch you just pressed. Inside is a secret cache which includes a BFG.
After crossing over the bridge raised using the blue skull key, an alcove will open back on the opposite side in the wall of the central building.
At the very end of the map, you must enter a green-stoned den to activate a skull switch that releases the Cyberdemon or Spider Mastermind and its comrades. One of the walls inside the den (the one where some Revenants come from, along the walls of the east stairs) is a fake: it hides a small room containing a Megasphere.
If you enter the water behind the door blocked by red skull bars (that are lowered by a switch that doesn't require a Red Key), without having lowered the sky wall first (by running over a trigger in front of the Red Skull key), you will become stuck and unable to progress any further or get back onto the walkway surrounding the structure.
Not so much a bug as an oversight: In the end of the intermission text, it is said that the player can hear "the stomp of a Cyberdemon's iron shoe". This creates a rather humorous end to the level if played on the "I'm Too Young to Die" and "Hey, Not Too Rough" difficulty levels as no Cyberdemon is present at the end.
According to the Text screen the player sees upon entering the map, this level does not take place on the Io moonbase like the rest of TNT: Evilution, but rather in a vacation resort on Earth (presumably the Caribbean islands).