This is a common element in anxiety dreams as the subconscious plays through various scenarios of what could go wrong. Dreams of twins do not necessarily indicate that you will be having twins. More likely you are meeting your child, who in the dream is the other half of you. Perhaps you worry you will be constrained by the role in some way. This is a common element in dreams.
Water represents emotion, the womb and fertility.
The behavior of the water is key. This is a common metaphor for the process of producing life. The whale is a powerful symbol of feminine power and creativity. If zoos figure prominently in your dreams, it could be a sign that you need to create more private space for yourself. And You Think Your Dreams are Bizarre . . .