The Legend of Zelda: Majora's Mask Walkthrough

Majora's Mask p.12

Clock Town Sewers
Ahead, there's a fork in the road leading to the left and forward. There's only one way you can go for now, so bounce from platform to platform until you get to solid land. Use A to spin just before you touch water and you'll zip across it really fast! This is handy for longer distances.

Once you get across, go to the left and you'll encounter your first enemy: a Skulltula. They're a bit harder to defeat than they were in Ocarina of Time, but you can still beat them up the same way. Wait for their back to be turned and hit them (in your case, with a bubble). Alternatively, this is a great time to use your Deku Nuts if you'd like to briefly stun it. Either show it who's boss... or simply walk around it in the shallow water. At the end, follow the narrow passage which leads to an open room. You can break the jars around here to get some Magic Jars (which restores your Magic Meter) and possibly some Recovery Hearts in case you were harmed by the Skulltula. The ladder in the center of the wall is blocked by another balloon, of all things. Honestly, the Bombers need a more high-tech security system... Pop this "obstacle" with a bubble and climb up the ladder.