No worries. With enough functioning gills, you don’t need to be a decent swimmer to breath under water. You can sit at the ground all day and still get enough oxygen. You might still get hungry and swimming can help to get food, but there’s also the option to filter feed so no worries there either.
Without gills, tho, it is highly advisable to be able to swim so you can reach the surface in time to breath.
Question: does that mean everyone with gills can breathe under water? I imagine they must be pretty decent at swimming, too.
No worries. With enough functioning gills, you don’t need to be a decent swimmer to breath under water. You can sit at the ground all day and still get enough oxygen. You might still get hungry and swimming can help to get food, but there’s also the option to filter feed so no worries there either.
Without gills, tho, it is highly advisable to be able to swim so you can reach the surface in time to breath.