A sense of isolation can be a theme. When near drowning, the character may feel alone in the vast expanse of water. There's also the theme of self - discovery. The near - drowning situation can make the character realize things about themselves, like their inner strength or their will to live. And of course, the theme of hope. Despite the dire situation, there's always that glimmer of hope that keeps the character fighting until they are saved.
Survival is a major theme. The character in the story is usually fighting for their life against the water, which represents a powerful and often unpredictable force. Another theme is fear. The fear of drowning is intense, and it drives the character's actions and emotions. Also, there can be a theme of rescue or salvation, like when someone or something comes to save the character from the brink of death.