World 6-6 (Super Mario Bros. 3)
From the Super Mario Wiki
The level starts with a Warp Pipe that sends Mario to the underground area. In the underground area, there are stairs which can be used to reach a small area with a jumping Cheep-Cheep, a Spike, and a Fire Flower. Next, there is a Wood Block with a Starman, another jumping Cheep-Cheep, and Piranha Plants. Next, there is a big underwater area with Cheep-Cheeps, 1-Up Mushroom, and another Fire Flower. In the end of the underwater area, there are a few Piranha Plants, which can be easily defeated with Fire Mario. After the underwater area, there are more Spikes, and a Warp Pipe which warps Mario to the goal.