A hot tub is read as relaxation shared with others, warmth, ease and a little indulgence. Who is in it with you points to whom you feel at ease with right now.
When this appeared in your dream, what were you feeling?
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.