Water either looks blue due the mineral deposits underneath it (The Azure Coast, for example) or the reflection of the sky in it. Any water that you find that is blue and sold as magickal blue water has been dyed.
Actually there is one water that is naturally blue due to the minerals it collects from somewhere, but the mineral source is depleting and so it's running out quickly. The well known "pink" flamingos are actually only pink because they drink that water and because of that it is only a matter of time before we no longer have pink flamingos, however their breed should not be going extinct anytime soon. There is no blue sea water that has not been dyed if it's not blue due to the reflection or similar minerals as you mentioned, Kikuyu, but there is still a little bit of naturally blue water.
I wouldn't call any water "spiritual" since to be spiritual it would have to be a little more living. There are water spirits, but they don't necessarily make the water spiritual. If you were referring to blessed water, Hannie, then I think you're supposed to bless it yourself or have someone you know bless it for you.