It is possible to get into Dungeon 4 without the Angler Key by using a Tracy Boost. Boost onto the angler keyhole and then walk off the ledge into the waterfall. The entire lower section of the waterfall does not have any collision, meaning you are free to move as if it wasn't there. This skips the Marin beach date, the walrus cutscene, and the Lanmola fight.
If you do Angler Key Skip, you won't be able to easily make it to Eastern Tal Tal Heights and Dungeon 7 due to the waterfall blocking your path. You'll need to get around that waterfall if you want to make it to those areas.