The gum that is used as explosives was not gum. If you pay attention in a previous scene you can watch Arthur roll out plastic explosive and cut it into gum size strips, then repacking them. The gum is essentially some plastic explosive disguised as gum.
The cream was just a shark deterrent.
Regarding the glass, most see through pools are made using some polycarbonate glass, which is also used in armored vehicles. I'm not sure wat exactly he used, but I'm sure there's some chemical that could be used in that way. After all, there is a huge amount of pressure on the bottom plates, and weakening the integrity does the job.