Today it happened the second time that a toon suddenly could not swim/dive anymore. My barbarian mystic walked into the water (beach where coldain and orcs fight each other) and started to sink deeper and deeper. Then she ran as if on solid ground, only blue sea all around her underneath and above. And no way to get up to the surface again. The only way to get out was porting. I don't know what happened. Like I said it is the second time now. The other alt got deleted because of this issue. Has anyone experienced the same bug?
Turn off the group spell Water Spirit, it causes the walking underwater. If you want to swim instead of walk, use the single-target Enduring Breath or the Fishbone Earring (from Hadden's heritage quest). The earring you put on, use, and then take off, it lasts one day.
Just as a suggestion, open your Knowledge book and take a few minutes to carefully read through all your spell descriptions sometime. You will discover that some spells do stuff you didn't even realize.
There are also a couple of items that grant underwater breathing but will cause you to sink. I will look them up and update here if I find them.