Altering “swamping” a bit to make this:
Create Waves (Su): Oceanus can create waves up to X feet high through force of will. This causes any sailing vessel within 300 feet to capsize if the character steering it fails a Profession (sailor) check (DC 15). A modifier applies to this check, based on type of ship, as follows: rowboat -2, warship +0, galley or keelboat +3, sailing ship +5, longship +7. Any creature flung into the water by a capsizing ship must succeed at a Swim check (DC 15) or immediately begin drowning.
Feel free to offer suggestions on changing the values or modifiers.