Hi Lisa!
Yes, sounds like you got it! Altogether a 5 day base ticket + Water Park Fun & More Option does total 10 visits.
The 5 day base ticket gets you 5 all-day visits to one the 4 major theme parks (Magic Kingdom, Hollywood Studios, Epcot, and Animal Kingdom).
The Water Park Fun & More Option matches your base ticket and gives you 5 additional visits to Typhoon Lagoon, Blizzard Beach, DisneyQuest, ESPN Wide World of Sports Complex, or green fees for a round of golf at Disney's Oak Trail Golf Course.
Unfortunately, you can't swap one for the other, but some guests do split their day up by starting the day at, say, Blizzard Beach, and finishing up at, say, Magic Kingdom. Just bear in mind that would be 2 tickets: 1 base and 1 Water Park ticket.
Have a splash of a time on your Disney trip!