Source: Tafsir al-Ahlam al-Kabir (Ibn Sirin)
The sea in a dream represents a powerful and just king, or the world with its horrors, trade, and dangers. Whoever sees the sea from afar will witness horror, strife, and tribulation. Whoever drinks all the sea's water will gain dominion over the world and have a long life. If it's salty, he will acquire unlawful wealth. Drowning in the sea indicates falling into strife, heresy, or the hands of the ruler. Swimming in it indicates delving into the king's affairs. Crossing from one side to the other signifies salvation from worry, grief, and hardship.
Source: Ta'tir al-Anam fi Ta'bir al-Manam (Al-Nabulsi)
The sea represents anyone with authority over people, like kings, scholars, and masters. Whoever sees himself wading into the sea will enter the presence of a king. Whoever urinates in the sea is persisting in sin. Whoever sees the sea raging and dark, it is a great strife and tribulation. A calm, clear sea indicates a just king, goodness, and prosperity. Catching fish from the sea is blessed, lawful sustenance.
Source: Al-Isharat fi Ilm al-Ibarat (Ibn Shahin)
The sea is interpreted as a king. If it is clear and calm, the king is just and good. If it is murky and raging, he is unjust and oppressive. Whoever sees himself drowning in the sea without dying will be immersed in worldly affairs, then be saved from them and reform his religion. Whoever sees himself drinking sea water will receive wealth from the king. Whoever draws water from it into a container will gain abundant wealth or a long-lived son.