The water is indeed fresh, though only time will tell whether or not it's hosting any parasites (unless you Purify it first).
Lerissa does not have purify water, she has create water. She will create water for herself to drink and watch the others for any signs that the stream is not good.
Ishirou sighs wearily as Lerissa makes her request. "I suppose I should do something to 'carry my weight.' Though I'm exhausted, so I make no guarantees I'll be of use to you.
"I realize the trek here was very tiresome for several of you. Once you get some food and water in your belly you'll begin to feel better and maybe we can see about taking the last watch so that you can get some rest first. I can tell already by your honesty that you are going to be a very useful asset."
"I thank you. Though I'm free in your eyes, the magistrates of Sargava will likely not see it that way once we reach Eleder."
"Whose to say we or you have to continue on to Eleder?"
Camp is established in short order, and a (rather bland) meal made from the rations scavenged from the wreck. As you cook it becomes apparent that the rations won't last long among the nine of you.
Abraxis nods. "Of course. With magic, anything is possible. My thought was if there happens to be a salvageable vessel, it would be along the coast. Also, I'm not sure if any shipping traffic passes close to this island, but if so we could possibly try to signal a ship."
How about some music?
"So this is the tale of the castways,
They're here for a long, long time,
They'll have to make the best of things,
It's an uphill climb."