Do you ever feel like you are drowning?

I can’t feel the bottom, I have no idea how deep the water is.  My chest constricts making it difficult to breathe.  I flip over on my back and reach my lips towards the sky above me to get more air.  I feel like I am suffocating.  I talk to myself, “you are okay!”  “You have enough air, float for a minute, catch your breath”.  The water is dirty and has a distinct smell of fish, I begin to realize that I have no idea what is in the water with me. “Stop thinking, I tell myself…just breathe, relax, focus.”…