Swamp Cave

Getting on the Ledge

Fire Rod Boost

Discovered By Viskiv And RheaultWnage

Lemon Boost

Discovered By RickWithAnH

Bomb Boost (Hard)

Discovered By ???

By doing a frame perfect bomb boost, you can get on the ledge above the boulder. This method is harder than the Fire Rod one and a bit slower as well.

Red Taros And Tornado Rod (Requires Energy Scroll)

Discovered By CloudMax, Refined By Koizata

You can clip on a ledge near Link's house with the help of an enemy, and use the south wall to reach another ledge just above the cave entrance, which is blocked by a Big Rock. (You will need the Energy Scroll and almost all of your Energy to reach that second ledge.) From that point, you can fall down and clip into the cave.

Since the enemy used to get on the ledge actually runs towards you and not away from you, you can simply lure him a bit and stand in that corner, use the Tornado Rod after taking damage and walk north a bit to get pushed to the right side of the torch. From that spot, just use the Tornado Rod once to get on the ledge.

Cave Entry Strategies

Once you've used one of the above methods to get out of bounds onto the ledge you can then maneuver Link to enter the cave. The Big Rock has very strange collision properties that make this inconsistent, but there are a few strategies that can help improve things. There is no consensus on which is the "best" strategy, so use whichever one works for you.

Bomb Push

Dashing

Tornado Rod

Walking