Gah - a solution with more questions. – EntropicLqd
Legacy:SlimeZone
From Unreal Wiki, The Unreal Engine Documentation Site
A SlimeZone actor, when placed into a sealed zone (see zoning), fills the zone with slime. The actor has things like the splash sound that entering the water makes all built in.
The SlimeZone actor doesn't provide any additional script, the same effect could be achieved by a normal ZoneInfo when changing its properties to the correct values.