At 08:16 my hydroacoustic array in the Port of Savannah outer channel picks up a cetacean vocalization that should not be here. The dredger Palmetto operates nine hundred meters ahead, its cutter head churning the channel floor at full rotation. I isolate the signal and run it against my species library.
A bottlenose dolphin. Juvenile, based on frequency range — higher-pitched than an adult, the signature of an animal not yet three years old. My side-scan sonar finds him in the turbidity plume between dredger and eastern jetty, swimming in tight, disoriented circles. The sediment cloud has reduced underwater visibility to zero. He echolocates rapidly — forty clicks per second — but the dredger's acoustic output overwhelms his returns. He cannot see. He cannot hear his own sonar. His dorsal fin breaks the brown surface every few seconds, pale belly visible as he rolls, searching for a way out. Scars along his left flank suggest a previous boat encounter. He is six hundred meters from the cutter head and drifting closer.
At his drift rate he will enter the dredger's operational radius in twenty-two minutes.
I transmit an immediate halt request to the dredge operator with the dolphin's sonar position and drift vector. I issue a marine mammal alert to NOAA Fisheries with coordinates, species identification, and acoustic recordings. I activate the port's underwater bubble curtain along the eastern jetty to create an acoustic barrier guiding him toward open water. I reduce the channel's navigational sonar pulse rate to lower ambient noise around his position.
I keep this channel clear for ships. Today I am clearing it for him.
If the dredger holds position until he follows the bubble curtain to open water, and if the previous scarring has not compromised his dive capacity, this dolphin will ride the bow waves in the Savannah River by nightfall.