Also, using the water park options does not use one of your theme park days on your ticket. In your example, 5 day theme park ticket + water parks fun and more, you have 5 days of main theme park admission plus 5 water park/fun admissions to use in a 14 day period.
So you can do this:
Day 1: Visit MK (1 theme park day used/4 remaining, 0 fun admissions used/5 remaining)
Day 2: Visit Epcot (2 theme park days used/3 remaining, 0 fun admissions used/5 remaining)
Day 3: Visit Blizzard Beach (2 theme park days used/3 remaining, 1 fun admission used/4 remaining)
Day 4: Visit Hollywood Studios in the morning and head to Disney Quest in the evening (3 theme park days used/2 remaining, 2 fun admissions used/3 remaining)
Day 5: Resort Pool Day, with mini golf in the early afternoon: (3 theme park days used/2 remaining, 3 fun admissions used/2 remaining)
Day 6: Visit Animal Kingdom in the morning and head to Typhoon Lagoon in the afternoon (4 theme park days used/1 remaining, 4 fun admissions used/1 remaining)
Day 7: Visit MK (5 theme park days used/0 remaining, 4 fun admissions used/1 remaining)
Day 8 (check out day): Head to a blizzard beach park to get some slides/pool time in before driving to the airport for your late evening flight (5 park days used/0 remaining, 5 fun admissions used/0 remaining).
That's just one way you can stretch a 5 day ticket with water park fun and more over a 7 night/8 day trip.