Question about Charlie and swimming

Ok this may have been covered before and probably has but I'll ask anyways. In season 1 Charlie is calling out to Jack saying there is someone in the water that needs help. He says he would help but he cant swim. (I'm obviously paraphrasing all of this). Jack swims out and discovers it is Boone, brings him to shore and goes back to get Johanna who doesn't make it. Anyways my question is this, later we see a flashback to when Charlie is a kid being taught to swim by his father and eventually he swims down to the Looking Glass station so obviously he can swim. This being the case why wouldn't he try to save Boone and Johanna after they first arrived on the island? Not the most interesting question to post I know but just something that's always stuck out to me.

Don't know if it makes a difference, probably not , but Charlie says "I don't swim.", maybe the "I don't swim" scene actually takes place after the Looking Glass drowning scene. Maybe his experience is the reason Charlie doesn't swim...I think there are several timelines (I've adopted this theory from Velleri)...you are right, this point does stick out!

DC

He was still using heroin at that point ... maybe he was high, maybe he couldn't swim in his weakened state, maybe he'd just puke if he tried from dope sickness, or maybe he was just scared. You make a good point though, I never noticed that before.

What gets me about this point is that when Charlie volunteers to swim down to the Looking Glass, Jack does not question it. He clearly heard Charlie say, "I don't swim" and I doubt he forgot that Joanna died after Charlie said that. Jack counted on the Looking Glass to be shut down so they could call the freighter, there is no way he would give that mission to someone who doesn't swim.

Then again Velleri ... I forget things about friends I've known for years ... so maybe it just didn't click in Jack's head.