Smartphones Lose Signal Underwater Fast

Smartphones Lose Signal Underwater Fast | Generated by AI

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Question: How do electromagnetic waves behave in water, and what happens to a smartphone’s signal if thrown into water inside a bag?

Answer:

Electromagnetic (EM) waves, including radio waves used by smartphones (cell signals, Wi-Fi, Bluetooth), behave very differently in water compared to air due to absorption and attenuation caused by water’s electrical properties.

Behavior of EM Waves in Water

Water (especially salty seawater) is a conductive medium, which causes rapid energy loss in EM waves.
Higher frequency waves (like those used by modern phones) experience much stronger attenuation than lower frequency waves.
Key factors:
- Seawater (high conductivity ~4 S/m): Extremely high attenuation.
- Fresh water (low conductivity ~0.01 S/m): Much lower attenuation, but still significant for phone frequencies.
Attenuation increases sharply with frequency:
- At cell phone frequencies (typically 700 MHz – 2.6 GHz for 4G/5G) and Wi-Fi/Bluetooth (2.4 GHz or 5 GHz), attenuation is very high.
- In seawater, attenuation at 2.4 GHz can exceed 700 dB per meter — meaning the signal drops to almost nothing after just a few centimeters.
- In fresh water, attenuation is lower (around 1–several dB/m at these frequencies), but still severe enough to block signals quickly.

Lower frequencies (like ELF/VLF used by submarines) penetrate much farther, but consumer devices like smartphones cannot use those.

Smartphone Signal When Thrown into Water (e.g., in a Bag)

Modern smartphones use high-frequency radio waves for cellular, Wi-Fi, and Bluetooth — all of which are heavily attenuated by water.

Practical outcome — Almost no usable signal underwater:
- In seawater (ocean, sea): Signal is lost within centimeters (often <10–20 cm) of the surface. Even just below the surface, connection fails.
- In fresh water (pool, lake, river): Slightly better penetration, but still typically lost within 10–50 cm depth (sometimes a bit more in very shallow submersion or near the surface with good alignment).
- Experiments and reports show smartphones lose cell signal, Wi-Fi, and Bluetooth almost immediately when fully submerged — even waterproof phones cannot maintain a connection underwater without special techniques.
A protective bag (e.g., waterproof pouch) doesn’t help with signal propagation — it may keep the phone dry and functional internally, but the EM waves still cannot penetrate the surrounding water effectively to reach cell towers or Wi-Fi routers.
Very shallow submersion (just a few cm, antenna near surface) might allow weak/intermittent signal in fresh water under ideal conditions, but this is unreliable and not practical.

In summary: Throwing a smartphone (even in a waterproof bag) into water will cause it to quickly lose all wireless signal (cellular, Wi-Fi, data) in both fresh and salt water. The phone might still work internally (screen, apps, etc.) if waterproof, but it will be offline until brought back near or above the surface.

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