Great sea has associations to the Unconscious and the Great Mother, but given that you are in your late teens, and the flooding image - the engulfing, swallowing tides - I would consider that it may be some kind of growth and regeneration that you may be reluctant to move in to?

Floods, like the biblical floods and primordial flood imagery of ancient times washed away old ways, and regenerates new Earth.

In psychological alchemy the flood is the Solutio, the stage where hot conflicts and emotions are dissolved, anticipating a new direction, imaged as coagulation, Coagulatio, again the new Earth - and all that;)

It is not necessarily a pleasant experience. You may be overwhelmed, but courage and a sense of adventure are the way to go... May be an exciting time of transition...

Interesting I did an I Ching reading in relation to you and this situation. It read first (5) CHUN: "Difficulty at the beginning, perseverance", then (11) TA'I: "Peace, the small departs, the great approaches" with the 5th line changing in CHUN, indicating that the difficulty at the beginning is caused by others interfering with your path, so that you must take small steps in the right direction, your own direction, to persevere, so that peace comes in your own individuation.