Alright. Suppose you're in a campaign where you're always around water, either under it or on boats. You might invest 1 point in swim per level anyway. Point is, you expect swimming to come up often, and for extended periods of time - as in more than 1 round per level. In that case, wouldn't Air Bubble be more efficient?
I mean, you'd use up 1 spell slot, as opposed to 1 arcane pool point (unless recalled). In combat, you would spend 1-2 arcane pool points to enchant your weapon... right? You only get so many per day.