Summary

This is not a cartesian diver. This diver toy works on a similar principle as the ballast tanks inside a submarine, although the air is not compressed inside. When you suck the air out of the tube, the diver will fill up with water and sink. If you blow air into the tube, the diver fills up with air and rises back to the surface.

See it in action : https://www.youtube.com/watch?v=inBiFN7ZPzk

The pla is quite light, so it needs a little weight to make sure it sinks. Place a pebble stone of about 2cm (20mm) in "diameter" into the diver body before the head is printed. You can pause the print on the printer, but it is better to set it into the Gcode and also enable the function to reprint layer after the pause, to prevent layer separation.

As a hose you can use any flexible tubing as long as it has the appropriate diameter, length, and it's clean enough. Fuel line, surgical tubing, fish tank air lines, valve rubber, anything, the more flexible, the better. In case of a thinner hose it is better to fit it inside a bigger nipple other than putting it onto a smaller one, it is structurally stronger that way.

The nipple needs to be glued on the top. The design includes several different nipple sizes. The names are coded so that the first number indicates the inner diameter, the second number indicates the outer (in milimeters).

The diver body can be scaled up. The nipple is simply glued on the top, it does not attach into a hole, so it will fit a bigger diver. However a bigger diver will need a bigger rock too.