Suggestion, if you poured the pre-ripened fish slurry into a soda can, froze it and then peeled away the can [mostly, I'd leave the top and bottom for structual reasons] you could use a black-powder soda-can cannon.

Although something like a t-shirt gun might work as well, and would be rather more man-portable for a quick getaway if necessary.

Although if you do go down the black-powder route... I'd suggest doing it on some holiday weekend that involves lots of fireworks, that way no-one would think anything of a few extra bangs.