When cast upon the sea (or large lake), the maelstrom spell punches a hole right through the Prime Material Plane into the Elemental Plane of Water. A huge whirlpool appears for 1d10 rounds, sucking everything close to it into the Elemental Plane of Water. At the end of that time, the rift between the plane's seals and the sea returns to normal.
The whirlpool has a dark center like a bulls-eye, surrounded by a ring of swirling water. The center has a 50-yard radius. The surrounding ring is another 100 yards wide (giving the entire whirlpool a 150-yard radius). All vessels within the whirlpool's center must make a sea worthiness check with a -20% modifier each round. Failure indicates that they are sucked into the Elemental Plane of Water. Success means they simply hold their ground; they have no choice but to hang on until the spell elapses or until they are sucked through. Vessels within the 100-yard border around the center must also make a seaworthiness check each round. Success indicates that they can sail under “adverse” conditions. Creatures and spells that affect water also may help them move from the area. Failure means they are dragged 20 yards toward the center.
An individual in the border area who is not aboard a ship is dragged 50 yards per round toward the center. Allies who control water or use magic may help; mere swimming has no effect. An individual in the center of the maelstrom who is not aboard a vessel must make a saving throw vs. death magic each round to avoid being sucked through the whirlpool. Success indicates the character holds his ground. Failure calls for another saving throw. If a second save vs. death magic succeeds, the individual is merely cast up somewhere else in the Prime Material Plane, with flotsam from a wreck. Characters from the same ship may be cast up as a group or scattered far apart (DM's option). Those who fail the second saving throw are dragged fully into the Plane of Elemental Water. Unless these individuals can somehow breathe underwater, or have friends among the marids near such an area, their prospects are grim: If they don't drown, they'll probably be enslaved by the marids.
The material component of this spell is a diamond worth at least 10,000 gp. The gem is crushed when the spell is cast.
Notes: Common for Sea mages or those from an Arabian setting; otherwise very rare.