Best I've come up with is one of those vacuum seal-able "space bags". Put the flash in there, tie a brick to it, and sink it to the bottom. I'm not paying $200 ~ $500 for an acrylic underwater flash housing. I'll be using it in a pool attached to the cheapo gadget infinity triggers (man, I hope they're powerful enough to work underwater) to shoot swimmers and divers. Thoughts... any better / safer ideas for reasonable costs?