I don't know who has a stash of liquid nitrogen just lying around their house, but these two must have a source. First, a cool billow of fog is created when liquid Ni is dumped into (on top of?) a pool.
Second, this group filled a contained with liquid Ni. It starts evaporating right away but the change accelerates into a controlled explosion (underwater). Probably not the one to try at home, IMO.
Makes these guys that just use dry ice (solid CO2) seem pretty lame, huh?