Each "Water parks & More" ticket gives you ONE admission to ONE of the extra parks. For example, if you went to Blizzard Beach in the morning, DisneyQuest in the afternoon, and Pleasure Island in the evening, you'd have used up 3 total admissions.
However, I believe that you can get your hand (or ticket?) stamped & reenter a park for the same day. For example, you can go to Blizzard Beach in the morning, leave & go back to your hotel in the afternoon, & come back to Blizzard Beach later that day, & only have used 1 admission.
Capiche?