Direct psychoanalysis:
Water and swimming are always related to the dreamer's feelings. If you dream that you are a good swimmer, it symbolizes his ability to control emotional scenes. If you dream that you are not good at swimming, it may mean that the dreamer must learn to deal with his feelings more positively and optimistically.
Subconscious spiritual symbol:
On the spiritual level, swimming in dreams symbolizes the ups and downs of feelings. Emotion is only one aspect of human existence, which can neither be overestimated nor underestimated.
Your mood is too low. Just improve it. That's what the unpleasant emotions in your heart bring to your dreams.