I kind of feel like, "I shouldn't have mentioned it"[:@]
If you can, replace the fuse with the igniter and call it good.
Otherwise I wrap the #30 wire around the fuse three times, and then clip off the extra fuse.
This is why all the safety measures, everything is either a direct ignition, or short fused.
(I was a little concerned that you might light a fuse and have the boat make a run for it.)
Aluminum foil may short out the electrical ignition, so it sounds like kind of a bad idea.
Water is not really the problem. Accidental ignitions are the concern. Providing enough
space on the vehicle, and not overloading it is a good preventative measure.
Several small display runs are always better than one meltdown.
Being able to keep count of what you triggered, and what actually fired will be easier also.
Assume it will be dark.
Color coded wiring or labels are a must so that everything can be connected, and
then goes off in a predictable and purposeful manner.
There can be a lot of wiring laying about and getting everything hooked up properly is a must.
Flipping a switch and saying oops is a no no.
Circuit testing can be done with just the igniters on dry land. This allows you to test the "hot wire" and make sure that when you
short a circuit, the igniter burns, and not your wiring. Also that the igniters you are shorting will burn through, and not keep the circuit hot if the switch is left on.
Being able to clear the firing switches, return the boat, and turn off the power in the water will save you if you have to return with a misfire, or live load on the boat. And that can happen quite often.