Blast spells are part of the elemental group of Magic combat spells in the standard spellbook. Elemental staves can be used to cut the costs of these spells. These are free-to-play spells. Like all combat spells, each damage point caused by these spells yields 2 Magic experience and 1.33 Hitpoints experience.. Each spell has a certain max hit, water blast is 14, earth blast is 15. Your gear and magic level determines your accuracy (check equipment tab). So you will be just as likely to hit with water blast as you will with earth blast, only earth blast can hit 15. That is all really. As for how often you hit high, there's a formula behind it.
Water Blast is a water-based blast spell in the standard spellbook, requiring level 47 Magic to cast. As an offensive combat spell it can only be cast on attackable NPCs, or other players in a PvP situation.. Water Blast is a medium level water spell. It requires a Magic level of 47 as well as 3 water runes, 3 air runes, and 1 death rune to cast.