Issues after leaving Dream Realm

Hey, I just left that hellscape and made it back, and I’ve got an issue. After I left the cave it put me in, I now have no exit out of the lake I found myself in. The only exit seems to be a waterfall, but since I don’t have the HM or the replacement yet, I am now locked in this place.

Is there something I’m too blind to see? Or am I permanently stuck?

You can just surf down the waterfall. Sometimes it’s finnicky and requires you to get a running start from above before being able to go down.