From the Introduction: Surface Tension is a standalone encounter designed for five characters between levels 6 to 9. The city of Stonegate was built on an expansive series of canals and aqueducts, used long ago to divert and carry water to neighboring cities. Now, the sewers are home to a variety of dangerous creatures, including a band of murderous sahuagin. The sahuagin climb to the surface each night, killing and kidnapping the city’s residents, who call for any brave enough to enter the aqueducts and dispatch this new threat.