There's no Papyrus function for it anymore. You can instead :
1) Create a Magic Effect on self with a Script with OnEffectStart/Stop EVENT 2) Create a Spell on self with this Magic Effect 3) Choose IsSwimming as condition for the ME in the Spell
I think I heard that the SKSE team said they would be able to implement console functions rather quickly. So if you can wait a bit I guess it will be implemented in the foreseeable future.
There's no Papyrus function for it anymore. You can instead : 1) Create a Magic Effect on self with a Script with OnEffectStart/Stop EVENT 2) Create a Spell on self with this Magic Effect 3) Choose IsSwimming as condition for the ME in the Spell This returns correctly if the Player is swimming.
That svcks... but you gave me a good idea for a new spell