I use wobbled glass in front of my flash to create a nice underwatereffect.
Not sure it's a purchase...I found it on a garbageheap and took it home....
Some glass building-blocks from the same heap are great in front of flashlights too.
Wouldn't mind seeing some results!
Canon 7D, T3i, EOS M, EOS 3, GoPro HD Hero & Hero 2, powershot sx230 hs, Canon 70-200 f2.8 L, Canon 100mm f2.0, Sigma 70mm f2.8 Macro, Canon 50mm f1.8, Canon 22mm f2.0, Sigma 18-50 f2.8, Tokina 11-16 f2.8, Lensbaby Composer, Holga HL