Event horizons are boundries in space-time in wormholes. The event horizon of the Stargate gives the appearance of water. Samantha Carter was amazed to see that the fluctuations in the event horizon were visible and appearing as ripples in water. (Stargate) (SG1: "Children of the Gods")
- In the original movie, the event horizon perfectly reflected what was in front of it, like actual water. This feature was not carried over to the series.