Can I repair a small crack in a small fibreglass pond with a hot glue gun?

I have a small crack in the side of my small fibreglass garedn pond. Water is going dissapearing at a slow but steady rate. Will I be able to repair it using a hot glue gun? Will that work?

Well, it'll work, but not long term. I suggest using epoxy to first close the crack, and then coat it in rubber cement to make sure it seals.

I would recommend a product called LEXEL. It is usually sold at Ace Hardware stores, and it is sold in tube form (as in caulking gun). This product is absolutley wonderful. It is toxic, so if you have fish or other waterlife in your pond, it may harm them.