Lower Water {Priest}

The lower water spell causes water or similar fluid in the area of effect to sink away to a minimum depth of one inch. The depth can be lowered by up to two feet for every experience level of the priest. The water is lowered within a square area whose sides are 10 feet long per caster level. Thus, an 8th-level priest affects a volume up to 16' x 80' x 80', a 9th-level caster affects a volume up to 18' x 90' x 90' and so on. In extremely large and deep bodies of water, such as deep ocean, the spell creates a whirlpool that sweeps ships and similar craft downward, putting them at risk and rendering them unable to leave by normal movement for the duration of the spell. When cast on water elementals and other water-based creatures, this spell acts as a Slow spell; the creature moves at half speed and makes half its usual number of attacks each round. The spell has no effect on other creatures.

Reverse: Raise Water

Its reverse, raise water, causes water or similar fluids to return to their highest natural level: spring flood, high tide, etc. This can make fords impassable, float grounded ships, and may even sweep away bridges at the DM's option. It negates lower water and vice versa.

[Player's Handbook]

Reversible

Sphere: Elemental (Water)
(Alteration)
Level: 4

Range: 120 yards
Components: V, S, M
Duration: 1 turn/level
Casting Time: 1 turn
Area of Effect: Special
Saving Throw: None

Material Components:
the priest's holy (or unholy) symbol and a pinch of dust