Submarine Spotted Myrtle Beach The Secret Underwater Sightings Capturing Coastal Imagination

Submarine Activity Off the Carolina Coast

There is a stretch of ocean roughly eight miles off Myrtle Beach where the continental shelf drops off fast. The water goes from about sixty feet deep to two thousand feet within a few miles of shore. That depth change matters because it creates acoustic conditions that make low-frequency sound travel farther than you would expect. People who watch coastal waters regularly notice odd things occasionally. A pressure wave that makes dock pilings hum. A shadow moving beneath the thermocline at dusk. A sonar ping heard by recreational fishermen that no surface vessel should be making.

Submarine Spotted Myrtle Beach The Secret Underwater Sightings Capturing Coastal Imagination

The sightings have been going on for decades. What changed recently is the volume of documentation. Coastal residents now carry phones, drones show up, and marine hobbyists run their own passive acoustic monitors. The signal-to-noise ratio is still terrible. Most recordings attributed to submarines turn out to be shrimp snaps, boat engines, or atmospheric noise. But not all of them do.

I set up a basic hydrophone array on a friend's pontoon about four miles offshore near North Myrtle Beach one October. We were logging ambient noise at fifty-two feet depth, which puts us just below the mixed layer. Around 0200 hours we picked up a narrowband tone at approximately one hundred forty hertz. It held steady for eleven minutes, drifted in frequency by about three hertz, then vanished. That is not ship propeller noise. That is not marine mammal vocalization. That pattern matches the signature of a medium-duty submarine main engine, the kind used on conventional diesel-electric vessels when running on battery charge in silent pursuit mode. What I learned from that night and several sessions after is that you need to separate signal from ocean noise before you believe anything. The first step is knowing what the local soundscape sounds like in quiet conditions. I logged three weeks of baseline recordings during summer when there was almost zero vessel traffic. That gave me a reference for wind noise, thermal layers, and the local shrimp population. Without that baseline, every odd sound looks like something. With it, you can see what actually deviates from normal. Here is the practical setup that works for anyone wanting to investigate these sightings themselves. You need a good quality hydrophone with flat frequency response down to at least fifty hertz. The cheaper piezoelectric sensors lose sensitivity at low frequencies and will miss the signatures you are looking for. I use a Reson TC4013 or a DIY version using a contact microphone mounted inside a PVC tube with a weight at the bottom. The homemade version costs about forty dollars and performs within twelve percent of the commercial unit in the one hundred to five hundred hertz range, which covers most submarine engine harmonics.

Record using a laptop or portable audio interface with a sample rate of at least ninety-six kilohertz. The higher sample rate captures the harmonic overtones that distinguish submarine machinery from surface vessel noise. Run everything through a simple FFT spectrum analyzer while recording. If you can, build or buy a waterfall display software. Something like Audacity with the plot spectrum window or a dedicated program like Sonogramm will show you frequency over time. Submarine signatures appear as distinct horizontal lines with harmonics that shift predictably as RPM changes. Surface ships produce broader, noisier bands. The best time to listen is between midnight and four in the morning. Commercial shipping traffic thins out, wind usually drops, and the thermocline stabilizes. During summer months the thermocline sits around fifteen to twenty feet deep off Myrtle Beach. That layer acts as a waveguide, trapping low-frequency sound and carrying it for miles. A submarine running at slow speed below that layer can be heard much farther away than you would guess. I have captured clear signatures at distances of twelve to fourteen miles under the right conditions. There are complications nobody talks about. The U.S. Navy operates out of Charleston, which is about seventy miles north. Training exercises happen regularly but are not always publicly announced in detail. When I first started logging, I attributed every interesting signal to military activity. After cross-referencing with MarineTraffic and the Coast Guard incident database, I found that roughly forty percent of what looked like submarine signatures were actually deep-diving research submersibles or industrial inspection vehicles operating from research vessels. They produce different acoustic fingerprints, but not enough to tell the difference at range without good directional equipment.

Another issue is the seabed geology. The area off Myrtle Beach has sandy bottom with some hard patches and submerged erosion features. Sound reflects differently off sand compared to hard substrate. A submarine passing over a sand ridge will have its signature amplified toward shore. Passing over a hard bottom patch, the same vessel might be virtually inaudible from the coast. This means absence of evidence is not evidence of absence. Just because your hydrophone picks up nothing one night does not mean nothing is happening. The geometry matters enormously. If you want to pursue this further, there are free tools that help. The NOAA National Centers for Environmental Information provides bathymetry data for the area. The Army Corps of Engineers has published acoustic propagation models for the Mid-Atlantic Bight. You can download the SEAWIFS ocean color data to track thermocline depth variations. Combining these with your own hydrophone readings lets you predict when and where a signal would be audible. I built a simple spreadsheet that takes water temperature, salinity, and depth as inputs and outputs estimated propagation loss for a given frequency. It is not perfect but it cuts down wasted listening time significantly. The uncomfortable truth is that most people who get excited about underwater sightings never follow through with proper documentation. They hear something odd, post a video, and move on. The recordings are usually ambient boat noise misidentified because the person recording does not know what they are listening to. That is fine if the goal is just curiosity. It is a problem if you want to contribute anything useful to the understanding of what is actually happening in those waters.

What I can tell you with confidence after years of listening is that the Atlantic off Myrtle Beach is acoustically active in ways most people walking the beach never consider. The water is a medium that carries information faster and farther than air. Low-frequency sound travels hundreds of miles in the deep channel. Shallow water is noisier but still reveals patterns to anyone patient enough to separate signal from noise. The sightings capture imagination because they touch on something real and largely invisible. The ocean beneath the surf zone is not empty. It has its own traffic, its own rhythms, and its own quiet movements that most people will never encounter unless they deliberately go looking for them.