First, and most importantly, go outside. This experiment is very messy.
Pour enough water into the canister so that it is about 1/3 full.
Break one of the Alka-Seltzer tablets in half.
Place the Alka-Seltzer into the canister, close the lid, and step back a safe distance (3-4 meters).
Wait a few seconds... and then watch your film canister rocket go bananas!
Hmm... it seems nobody's added a conclusion for this experiment yet. You can suggest one here.
In seahorses, it's the male that carries the babies and eventually gives birth.