Why don't you get the 10 day pass and add the water park fun and more option. You have your arrival and departure days that may or may not be park days, plus your sea world day. these options give you something else to on non-park days.
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Water Park Fun and More Add-On Option
For Disney fun beyond the four theme parks, this option provides the choice of admission to Disneys Blizzard Beach water park, Disneys Typhoon Lagoon water park, DisneyQuest, a round of golf at Disney's nine hole Oak Trail Golf Course (Tee times required: 407-WDW-GOLF.) , entry to the Downtown Disney **Pleasure Island nightclubs or Disneys Wide World of Sports Complex. The Water Park Fun and More add-on visits are equal to the days of your ticket with the exception of the 1 Day which gets 2 Water Park Fun and More visit. Beyond that, a 2 Day gets 2 Water Park Fun and More visits, 3 days 3 Water Park Fun and More visits, etc.
**The nightclubs at Pleasure Island are closing on September 28.
Park Hopper and Water Park Fun and More -
To capture all that Walt Disney World has to offer, this ticket combines the benefits of the Park Hopper Option and the Water Park Fun and More Option. Number of Plus visits to Water Park Fun and More attractions varies with length of ticket