Quick wins for a faster PC:
Clear out junk files and repair common Windows errorsFree Scan →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Repair Windows errors before they cause bigger problemsFix Now →iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
Acoustic communication is generally the practical choice for sending data between submerged devices. Sound can travel through seawater over useful distances, while ordinary radio-frequency signals such as Wi-Fi and cellular are strongly attenuated. Specialized very-low-frequency radio can serve limited underwater uses, but it is not a general-purpose substitute. Acoustic links also have trade-offs: modest data rates, propagation delay, noise, multipath, and changing channel conditions.
How do underwater acoustic communication and radio compare?
The main difference is what propagates effectively through water. Acoustic systems encode data in sound waves; RF systems use electromagnetic waves, whose attenuation in seawater depends strongly on frequency. For links between submerged sensors, vehicles, or other nodes, acoustic equipment is usually the workable starting point. RF becomes relevant in specialized low-frequency applications or when a relay carries data across the surface.
| Decision factor | Acoustic communication | Radio-frequency communication |
|---|---|---|
| Underwater reach | Common choice for submerged links; achievable distance depends on the sound channel, equipment, and deployment conditions. | Strongly frequency-dependent attenuation limits ordinary RF. Lower frequencies penetrate farther, but require specialized systems. |
| Data rate | Usually constrained, with usable bandwidth tending to narrow as range increases. Sonardyne lists up to 9,000 bps user data rate for its Modem 6 family; that is a manufacturer specification, not a typical rate for all acoustic systems. | Terrestrial RF performance does not carry over underwater; usable rate depends on frequency and the link budget. |
| Propagation delay | Sound travels through seawater at about 1,500 m/s, so delay grows with distance. | Electromagnetic propagation is much faster, but underwater attenuation limits practical links. |
| Reliability factors | Multipath, ambient noise, and changing water conditions can affect reception. | Water conductivity and the selected frequency strongly affect attenuation. |
| Typical equipment | Requires suitable acoustic transducers and modem hardware. | Underwater use calls for specialized low-frequency equipment; ordinary handheld radios are poor substitutes. |
| Connection to the surface | A surface modem or relay commonly passes data from an acoustic subsea link to a radio link above water. | Radio can carry data through air from a surface relay to a vessel, shore station, or other receiver. |
Can radio waves travel underwater?
Yes, but “radio” covers a broad range of frequencies, and seawater does not treat them alike. Higher-frequency signals, including those used by ordinary Wi-Fi and cellular systems, are attenuated too strongly to serve as dependable general-purpose underwater links. Very-low-frequency bands can penetrate farther, but the equipment and operating constraints make them a specialized solution rather than an underwater version of everyday wireless networking.
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →An IEEE 2025 conference survey gives approximate examples of about 30 m penetration for VLF and several hundred metres for SLF/ELF. These are reported examples, not universal guarantees: actual performance depends on seawater conditions, frequency, antenna and link design. The evidence does not establish one depth-versus-data-rate curve that applies to every deployment.
#1 Best Overall
Why is acoustic communication the usual choice?
Sound remains useful over underwater distances where ordinary RF is heavily attenuated. NOAA gives the speed of sound in seawater as about 1,500 m/s. At that speed, a signal takes roughly five seconds to travel 7.5 km one way, before processing or protocol delays. That figure is an arithmetic illustration based on NOAA’s sound-speed value, not a modem benchmark.
Acoustic propagation can extend much farther in favorable ocean paths, but long sound propagation is not the same as a reliable digital data connection. A modem must receive and decode a signal well enough to complete its protocol exchange, under its particular noise, multipath, geometry, and equipment conditions. NOAA notes that sound travel distance varies substantially with water temperature and pressure; temperature, salinity, and pressure influence sound speed, and refraction can shape the sound path.
What limits an underwater acoustic link?
- Bandwidth and data rate: Underwater acoustic channels have limited bandwidth. Engineers balance range, carrier frequency, absorption, noise, and power, so longer-range designs commonly accept lower throughput.
- Propagation delay: Sound is slow relative to electromagnetic signals. The delay can matter for interactive control, acknowledgments, and coordination across long distances, even before device processing and network protocol time are counted.
- Multipath and changing conditions: Reflections and rapid channel variation can complicate signal reception. Ambient noise and local water conditions also affect link quality.
- Deployment-specific performance: A modem’s range depends on the model and operating scenario. Do not infer a digital communication range from how far sound can be detected by a hydrophone or how far whale calls may be heard.
How do submerged devices connect to a vessel or shore?
A common arrangement uses acoustics for the underwater portion and radio for the above-water portion. A submerged sensor or vehicle sends data acoustically to a surface modem or relay; that surface equipment then forwards it by radio to a vessel or shore receiver. Crossing the air-water boundary is a separate link-design problem, not proof that ordinary radio works through the water itself. Specialized cross-medium approaches have also been studied, but they are not a blanket replacement for this relay pattern.
What equipment should a deployment use?
Choose around the mission rather than a headline maximum. Before selecting hardware, define the operating distance and depth, amount and frequency of data, acceptable delay, waterbody and expected acoustic conditions, power budget, installation constraints, and whether a surface relay is available.
- Check the modem’s supported frequency band, user data rate, depth rating, and stated range for the exact model.
- Confirm that the transducer, vehicle or sensor interface, power supply, and communication protocol fit the rest of the system.
- Ask what conditions and configuration underlie any range or rate claim, and whether stated maxima can be achieved together.
- For RF, verify the frequency-specific underwater link design and specialized antenna/equipment requirements rather than relying on an ordinary radio’s air-range specification.
For example, Sonardyne describes its Modem 6 as an underwater acoustic modem for subsea-to-surface data transfer, including sensor-data retrieval and command/control. The manufacturer lists user data rates up to 9,000 bps and depth ratings up to 5,000 m for the family and specifications shown. Those figures are not evidence that maximum rate and maximum depth are simultaneously available in every configuration; check the exact model and current datasheet for a real deployment.
Quick Recap
Sources
- NOAA: How far does sound travel in the ocean?
- IEEE overview of underwater communications
- IEEE 2025 conference survey on RF penetration examples
- Sonardyne Modem 6 product specifications
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
