Masters now have a series of high quality boxes, waterproof to 30m. They are branded "Otter Boxes".
I bought 2 "size 3000" boxes and a size 2000 in clear. The 3000 has internal dimensions of 7.64"x3.72"x1.23" (according to the label) and the 2000 is 5.7"x3.1"x.97".
After inserting sliced foam, these larger boxes are the new homes for my large snapper flies (squid and crustacea), while I'll use the smaller box for smaller flies when wading.
These boxes look boom proof to me!

A selection of squid and crustacea ready for a fishing trip. (50c piece for scale.)

These two boxes were $25 each, while the smaller one was $19
Cheers,
Graeme