Hi Emily,
Thank you for stopping by the Disney Parks Moms Panel with this question about the Water Park Fun & More Option! I'll answer each of your questions in turn.
Unless your multi-day theme park ticket has the Park Hopper Option, you will not be able to visit two theme parks in one day.
Multi-day theme park tickets are valid for admission to any one of the four theme parks per day. You can leave and return to the same theme park, but you cannot visit a second theme park on the same day, even if you have an extra day remaining on your multi-day ticket.
However, with the Water Park Fun & More Option, you can visit a water park and a theme park on the same day. For example, you could start your day at Disney's Typhoon Lagoon Water Park and then head to Magic Kingdom Park later that evening.
With a five-day base theme park ticket that includes the Water Park Fun & More Option, you will get admission to any one of the four theme parks per day
plus you will have five "Fun" visits. With your Fun visits, you can visit
Disney's Blizzard Beach Water Park,
Disney's Typhoon Lagoon Water Park, ESPN Wide World of Sports Complex, Winter Summerland Miniature Golf, Fantasia Gardens Miniature Golf, or Disney's Oak Trail Golf Course (one round). You can visit both water parks on the same day, which would use two of your Fun visits. You can spread your Fun visits out over the course of your vacation and visit the theme parks and water parks over ten days (five theme park visits + five Fun visits)! As you can see, the Water Park Fun & More Option is a terrific value and gives so you many choices on your vacation!
Wishing you a magical vacation, Emily!
Erin