Purple Sea Bubbleweed
The purple sea bubbleweed split from purple bubbleweed. Even though its line went to land, it still needed most sand, so it was not too much of a stretch that it went back into the water. Since iuncusaquatilis lemniscus went extinct during the solar flare disaster, purple sea bubbleweed took its niche. But like purple bubbleweed, it still has hydrogen filled seed bubbles. These bubbles also keep the leaves upright and it buoyant in the water. This works much like Earth's kelp, except when its bubbles fall off they actually float up and out of the water into the air. They then land back in the sea. They asexually reproduce with these bubble seed/spores.