I accept that this is a problem but I’m not going to do anything about this for many years. The player is represented in the prototype by a single collision capsule. The species skin generation is missing so there’s no way anyone would be able to really fix the physics before the actual shapes of the species can be generated.
If you can’t get on land, then you probably put in an axon before that, which can result in a bug where you accidentally awaken underwater and get stuck there. This will be fixed in the next release (the fix is already merged):
For now you can work around the bug by not using the axon organelle before you get on land.