Releases

Releases: A common task is to recover an object that is weighted down or anchored to the seafloor. To do this without divers or an ROV , a release is utilized. There are several types of releases.
Galvanic releases rely on seawater to corrode a wire or link. Generally these are inexpensive but the rate of corrosion can differ from place to place and thus the time to release is not controlled with great precision.
Burn wire releases utilize a timing device to activate an electrical current that will burn out a wire, which in turn causes the payload to be released.
Timed releases use some sort of mechanical device that is activated by a timer.
The drawback to all these methods is that the release time must be set before the device is deployed. Thus, there is no way to change the release time if inclement weather or other issues change one’s schedule. Acoustic releases solve this problem, because they are activated when they receive an acoustic tone of a specific frequency. Typically this is done by someone in a boat who is in the vicinity of the object to be released. Acoustic releases are available with different frequencies that have different ranges. Other considerations in selecting a release are battery life, depth rating and strength rating. More sophisticated acoustic releases use a coded pulse to prevent being accidentally activated if a passing ship or some other source in the area happens to emit noise at the release frequency.