The Problem

There are now more than 135,000 free-divers from 9 developed nations, driven by an explosion in classes and on-line tutorials. In the US alone, 1 out of 1600 free-divers will die participating in their sport. Unlike SCUBA divers, free divers tend to be cost conscious and prefer to be unencumbered by equipment, typically diving with only a mask, snorkel, wet suit, fins, knife, and weight belt. Often they tether a dive buoy to their spear gun. A typical dive cycle is under two minutes. A leading cause of death is shallow water blackouts. Other causes include underwater emergencies such as entanglement, blood loss, loss of vision, and hazardous encounters with marine life. Since irreparable brain damage begins within 6 minutes, promptly alerting the dive buddy to the emergency situation is critical to reducing the death rate.





The Solution

Provides an audible and visual alarm to your dive buddy when you are in danger

Attaches to your dive float to replace your existing flag holder

Economical and doesn't add any bulky equipment



  • Audible and visual alarm sounds to alert your dive buddy that you need assistance.
  • Audible alarm sounds both above and below the water.
  • Selectable time delay avoids inadvertent activation and spurious alarms.
  • Pre-alarm (pulsating beep) warns you to silence the alarm if you are not in danger.
  • Grip and release to sound alarm immediately if you are entangled (or have another underwater emergency such as blood loss, loss of vision, or a hazardous encounter with marine life. (This function currently in development).
  • Economical. Additional cost to you is less than $500.
  • Un-encumbering. No extra equipment to wear. Most of the unit attaches to your dive buoy. Underwater cable replaces your float line. Release switch is embedded in your speargun handle (or can be attached).
  • Hand-held switch will soon be available for use when not spear fishing.



  1. Verify your selectable time delay (not on prototype)
  2. Turn power switch on (moves up)
  3. Grip your speargun handle
  4. Enjoy your free dive
    • If grip released, pre-alarm (pulsating beep) sounds after selected delay
    • After 5 more seconds, alarm will sound
    • To silence the alarm, regrip the handle and continue to hold.
    • (eventually) Grip and release several times rapidly to sound alarm immediately




  1. Flag base to mount flag pole with light.
  2. Upper case lid closes and seals tight.
  3. The brains of Sea Siren including the above water audible alarm.
  4. Long life rechargeable battery.
  5. Pistol grip with release switch. Replaces yours or switch can be velcroed on.
  6. Lower case mounts with...
  7. strap holder.
  8. In water alarm:
  9. Not shown: Float line with electrical connection connects the Sea Siren to your speargun


Advantages of Freediving over SCUBA Diving.

As a recreational activity, freediving is celebrated as a relaxing, liberating and unique experience significantly different from scuba diving. Some advantages are:

  • less equipment to wear
  • greater mobility and speed
  • lower diving costs
  • shorter preparation time
  • no decompression time for deep dives
  • greater visibility due to a lack of exhaled air bubbles
  • no distracting sounds like regulator breathing
  • greater time in the water since air tank refills are not needed


Start at 4:35




This is a design project done as part of Engineering Design and Development, a PTLW course, core training and does not represent a product that is currently marketed.
© 2015 Jordan O'Boyle, Brian Roache, Paul Wiedorn.