The rear wheels drive a propeller and the front control a rudder... and it's been invented a couple of times (thanks to Steve for the Patents!)

https://www.facebook.com/photo.php?fbid=10109855407022140&set=g.712743252141034&type=1&ifg=1

https://patents.google.com/patent/US1804262

And Steve found that someone patents a similar vehicle powered boat about every 10 years, even for motocycle and snowmobile