Sorry, my names aren't brilliant
The ocean around the target become frozen and solid, covered with ice several feet thick. Ships become trapped in it helpless, unable to move. Usually used against enemy ships; however, if the ocean is frozen between your ships and the enemy's, the ice is strong enough to support people running between the ships to board.
Rite of Spring
Can only be cast on previously alive vegetable matter (e.g. wood). If cast on a wooden enemy ship, leaves, stems, branches and roots will sprout from all parts of the wood, growing rapidly, obstructing movement, causing havoc and, if unchecked, threatening the very integrity of a ship. A ship could literally tear itself apart.
Alters the direction of gravity in a largish region, by perhaps as much as 5-10 degrees. Ships and water act as if on a slope, rushing downwards to find a new equilibrium. More than one of these can be cast at once to create a "valley" in to which the enemy ships will be hurled, to crash in to each other and be overwhelmed by the waves of water pouring down after them.