Spells that conjure an expanding circle of material.
A spell that creates a large orb of rapidly expanding water at melee range. The flow will keep going until it is stopped by terrain or other solid materials.
As water is generally harmless to the player, this is the safest circle conjuration spell to use. There's a risk of drowning, however, due to the large amounts of water created.
With the Electricity Perk, the player can quickly flood a wide area and electrocute everything inside, without fear of electrocuting them self.