Check out this video tutorial to see how to conduct a magic floating boat science experiment.
Two little mad scientists investigate Helium and Sulfer Hexafluoride. Rosie and Anna study Helium, a gas that is lighter than air, and Sulphur Hexafluorid (SF6), an inert gas that is much heavier than air. Just like the Internet famous University of Bonn Physics Department Demonstration (Physikshow Uni Bonn) and Science Day displays they are able to magically float a small ship made of aluminum foil above the ground on a blanket of gas and then sink it by pouring the gas into the boat with a beaker. This is also known as the invisible water effect. Helium has the well known effect of raising the pitch of the voice. S6F has the opposite effect and lets you say things like "You're crazy man" (like Will Farrell in the movie Old School) or copy Darth Vader, "Luke, I am your father" (like James Earl Jones as Darth Vader in Star Wars).