......their website is a little thin on details.
I have been on duck boat tours in DC, Cape Cod, Austin, Seattle, Ketchican and San Diego (twice). My family & I have enjoyed the first tour we took so much, we look for duck boat tours when ever we are traveling to a place with water nearby.
Generally speaking, Duck Tour narrators are silly and light-hearted while still conveying interesting information. Kid friendly bad jokes and puns abound. I think that it is mandatory to at some point hear the Gilligan's Island or Jaws theme song.
The tours start on land and at some point spend time in the water. Our 'in the water time' experiences have been any where from 15 minutes to darn near an hour. Once we were lucky enough that the driver/captain let the kids on board take turns at the wheel while in the water.
While some duck boats are built for just for the tours, most duck boats are re-purposed DUKWs
From Wikipedia:
The DUKW (popularly pronounced "duck") is a six-wheel-drive amphibious truck that was designed by General Motors Corporation during World War II for transporting goods and troops over land and water and for use approaching and crossing beaches in amphibious attacks.
I told my seven year old (8 on the cruise) that there was a duck boat on St. Thomas and he started dancing.
The reviews I was able to find on Cruise Critic were positive, the only complaint was the heat. I think by going in the morning, that won't be an issue.