Artemis is definitely staying above water. She could fly after them and watch from above.
Here we are!
Buried deep within the development thread. She can cast both without risk of outright failure if I'm remembering the casting rules right, assuming a simple die, but she might need to rest in between castings to recover fatigue. I don't have time now, but I'll get everything organized better today. She'll also cast Wizard's Sidestep.