hi, i'm making a diorama of a panther that has slight into a river. He's carrying some ammo boxes and two of them are broken open. Now my question is, do they float or sink? I know that they are from wood, but maybe it's to heavy to float.

If they have any ammo in them my bet is on sinking. If they have spilled the ammo, they would float. Upside down they would trap air, right side up they should displace enough water to float for a bit.

was going to say the same thimg as slodder said. If the box is empty, it will float for a little bit before getting water loged and sinking.

wood is wood anyway and if the box is empty will float for sure.
if the box is open and the back is intact it will be like a boat, so maybe would carry some ammo, too

the pieces of wood that the box is made are not usually very well putted together or sealed or anything , so even if its empty it will flow at first but after some time it will start takin water into and half sink till it sinks all of it

Wooden ammo boxes will float when empty.
Metal boxes with ammo inside weigh like a brick, so they reach the bottom. Metal ammo boxes (MG bullets) would also float when empty. Some of them are sealed when closed, and could drift for a very long time. Only a few percent of the box would stick above the surface, though.

some may float just under the surface of the water with a little air as this is the case of containers which get lost at sea apparenty these are a dangerous shipping hazard there
was a news article some time ago on it hope this helps a little but if they are wood the case will swell up due to the water getting into the wood thus sealing any gaps

Perhaps the safe answer is to put them in shallow water, perhaps near the edge of the banks... they could be partially submerged if so desired, but even a box full of ammo could be shown if the water isn't deep.