Yes, really. A cool thing called total internal reflection is applied when pointing a laser beam through a container of water. When light travels through water, it’s slowed by the heavier particles in water, as described here. Thus, the laser beam effectively gets “trapped” in the water.
25 science facts you never learned in school
The world has many strange but amazing true facts making it a really marvellous and mysterious place.
A laser can get trapped in water