Mushy waves are slow, crumbly, and lack power, often from a weak swell or a gently sloping bottom. They’re great for beginners on longboards. Hollow waves, or barrels, are the dream—steep, fast, and with a pitching lip that creates a tube. They come from powerful swells hitting a steep reef or sandbar. Mushy is for cruisy turns; hollow is for getting shacked. You need different boards for each, and a whole different mindset when the waves start throwing.