I've never grown one from seed, but I don't think I would attempt complete submersion in fear of everything floating away/around. Maybe bring water level up to the surface and have bagged or whatever to maintain that level?
Currently thinking of a peat and sand slurry in a petri dish until it sprouts. I will be doing some Byblis Aquatica at the same time. Then transfer into clear glass and plastic containers for full growth. Some of the Byblis may end up outside in my mini bog
Here is what happened when I first tried to fill a container with water and soil, lol!
Probably both. Naturally it grows on lake shores, meaning that it is subject to submersion depending on rain and subsequent water levels.
Folks I've talked to recommend growing it in a pot with a water dish taller than the pot to allow for submersion.