As always, Wikipedia has more -- because that is what they do.
https://en.wikipedia.org/wiki/Ford_GPA

Also ...
The Amphibious jeep story
http://www.m201.com/GPA.htm

Alternate title, even if a bit inaccurate.

In 1951, Ben and Elinore Carlin set off on their wedding journey, circumnavigation of the globe in a surplus Ford GPA amphibious jeep he named the Half-Safe. George completed the journey in 1958, but the marriage was finished three years earlier.

but I had no idea that the US had an amphibious Jeep! The most famous "seep" of WW2 is the German "Schwimmwagen", but this looks like a much better vehicle!

It's a Ford GPA. Was too slow and heavy on land and wasn't great in lakes or ponds. In moving water it was very poor. Too slow on water as well and sat too low.

Some friends of mine have five military Jeeps, two or three of them made by Ford. One odd thing about them is that most of the bolt head have the Ford script raised on them. When they show it, they're amused by how many people walk to the back to see if it has a propeller. They always joke that they should charge a quarter each to go back and look. I'd tell you if it does or not, but you're going to have to look if you see one at a show.

In high school, I worked for a lady who had a Willys Jeep like this one:

It had a sealed engine that could be retrofitted with a snorkel. Other features included windshield wipers that worked by a passenger swinging a lever back and forth, and a super-low gear that could make the Willys climb at a very steep angle.

(I always hoped to buy the Willys from her, but she sold it before I got my driver's license.)

I grew up in the Toledo area, and we passed the Willys Overland Administration Building! many times before it was imploded in 1979.

And she can float my boat anytime.