A swimming pool is water with edges, so it is read as feelings you can explore in safety. Clear water points to ease with your emotions; a dirty or empty pool to feelings that have been neglected. Diving into a pool is read as plunging into a situation with confidence, while being unable to swim in it suggests feeling out of your depth in a familiar place. A crowded pool points to social pressure. Swimming alone is taken as calm time with your own feelings.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.