Hi everybody,
for my project I need a waterproof case which floats.
Does anybody can someone give me a recommendation?
Best regards
Hi,
A boat ? 
[serious mode on]
If you want a professional enclosure I'd check on IP-rating and buy one suitable for your project. If you want to build something yourself, tell us more about your project, size, conditions, how it's powered etc.
Any waterproof case will float if the total weight is less than the same volume of water it displaces. If the volume of the outside of your case is 5000 cc (5 liters) and the case plus contents weighs less than 5 kilograms it will float.
That's one ounce of weight per fluid ounce of volume.
Why not a jar with rubber gasket on the lid.
I'm really cheap. Dollar store Tupperware is what I use unless I am being paid for fancier.
You would be surprised how much serious engineering gets done in tupperware lunch boxes.
My project box was watertight and would float before I made modifications to it. It is a "Utility Box" that I got from Home Depot for around $30 and is used in the field for maintaining electronics in the elements.
There are also mounting tabs that don't compromise the integrity any. I'm sure the box would float, but I don't know of it's buoyancy.
I bought a gasketed tackle box from West Marine. It has latches that clamp tightly and a thick gasket that provides an excellent seal. For extra protection I bought a big bag of sillica gel packets (ebay) and put several in the bottom of the box. I used electricians putty(Ace Hardware) to seal the hole for the wires.
