Here is my “5 Buck Boat”. I decided to start with a known quantity of coinage. So, in this case 20 US quarters totaling 5 bucks.

I had to design/build this twice (see pictures). But, the first attempt highlighted two things. One, I underestimated the amount of displaced water needed. And two, I was storing my coins too high creating balance issues.

So, my second attempt was much better. Just enough displacement to store the 5 bucks. Once I was solid on floating the coins I added a deck, antennas, cabin, tire bumpers and a couple anchors.

Check out the instructions!
Thanks, Reamo

Couple things to note:

1. Bond parts using Acetone.
2. Print and build, no sanding, drilling or painting required.
3. Antennas can be printed, I just found some wire (paper clip, needle, thread of material from the print head, or whatever you find works).
4. Doors and windows colored in with Sharpie.