a marine biologist kneels by the water's edge, dipping a testing device into the murky water while her colleague watches closely. She pulls up the device and examines the readings with a focused expression. The water around them shows clear signs of being neither fully fresh nor fully salty, with different colored streams swirling together. Her colleague points toward the mixing currents where river water flows into the tidal area. Salt-tolerant plants grow along the waterline while both freshwater reeds and seaweed are visible nearby. water that is slightly salty from the mixture of river water and seawater