A Ruler Swimming in a Turbulent Sea
Scholars have interpreted that a ruler seen wishing to swim in a turbulent sea may indicate engaging in battle with another king. If the ruler crosses the sea by swimming, it might signify killing that king. The drying up of any sea, river, or valley is interpreted as the demise of a state associated with it, and if the water returns, so does the state. It has been said that escaping water by swimming before waking up is better than waking while still swimming in it.
Per Ibn Sirin's Muntakhab al-Kalam fi Tafsir al-Ahlam