Agree with your schedule. It is sensible to go into waterpark in the morning and later to sea aquarium. You could stay in sea aquarium with longer opening hours too.
Last time we went there with a 3-day package from Friday till Sunday. There were crowds of people everywhere. We went into sea aquarium at 5 to avoid the long queue and enjoyed the visit after 7 on a Saturday.
Where did u brought the ticket if u use the secret passage to water park ? Should I brought it from the main entrance in advance or simply brought it from the hotel front desk ? Thx !