Best Practices in Recovery
This is the first of a multi-part blog series that describes some of the tools we use in our recovery searches. We’ll start today with an overview of our most basic tool: the tender-directed search.
Recovery diving, also called public safety diving, is not what many people imagine it to be. We don’t see a lot of colorful fish and moving kelp forests - generally we can’t see anything at all! Often, our visibility is limited to a few inches, or less. And our mission is to find something, or someone, and make a recovery, without knowing exactly where our target is located. How is this even possible, since we can’t see a thing in the murky water?
A team approach
The best approach to this problem is to work as a team, in a process called “tender directed diving”. In this scenario, The diver does a thorough search using their hands to feel through the dark waters, but they’re directed by a person at the surface, the “tender”, who makes sure they’re covering the target search area thoroughly, and at an appropriate pace. We affectionately refer to our diver as “the dope on a rope”, because they’re attached to a rope and a harness, and following the instructions of the tender. The diver’s job, then, is to keep that line taut, move at the direction of the tender at an appropriate pace, and thoroughly search for their target as they move. The tight connection between the tender and the diver enables us to know exactly where the diver is searching.
Divers and tenders use a standardized set of signals to communicate through tugs on the line. These tugs are sometimes called “bells”, as if one is ringing a bell. So, a tender might send “1 bell” to tell the diver to stop and make the line taut. The diver always returns the signal to acknowledge the communication. A diver might send “2 bells” to tell the tender to make a notation at the location. Perhaps it’s something that merits a second search, or an entanglement hazard. Tenders also acknowledge communications.
Recording the search
As the diver proceeds through the search, it’s important to keep a record of where they’ve searched. It’s vital to know what has and has not been searched. You can imagine that a diver, operating without surface direction, could just wander around aimlessly and search the same area repeatedly. The individual keeping records is called a “profiler”. Operating as a team, the diver and tender, aided by the profiler’s collection of records, can efficiently search an area and have some certainty about what areas still need to be searched, and where our target is NOT located.
A typical search profile might look like this. This is an arc pattern, where the diver searches in a windshield-wiper shaped pattern, and the tender stays in place, directing their movements. The purple dot represents the tender, while the shaded area is the area our diver has searched. The green dot represents where they started, while the red dot is where this diver finished. A couple of other numbered dots on this diagram represent notations that our profiler has recorded. Arc searches are one of our staples. And the profile is so important, we developed our own software to keep accurate records.
This search was conducted from a dock, where the line was between 37.5 and 42.5 feet, with a lot of overlap between the diver’s passes. This is appropriate when we’re searching for something that’s fairly small. We stretch out the passes a bit when we’re looking for a person, and even more when searching for a car. The actual search area for this diver looks like this from a satellite view:
When we combine our search views together, we can create a very clear picture of what has been searched, and what remains. Operating as a team is critical, and each position is equally important: diver, tender, and profiler. A diver operating alone is about as useful as a profiler without a diver.
Adapting to the situation
It’s important to recognize, though, that the diver’s job can be dangerous. They rely on a bottle of air and a SCUBA regulator to breathe. So it’s also important to make sure safety measures are in place to protect our diver. We try to have three divers ready to go: our primary search diver, a backup, and a 90% backup, just in case something goes wrong and our backup diver has some problem when they’re needed. Together, an experienced team that includes resources for diving, tending, and profiling, along with mission planning skills that come with years of experience, can safely execute a search efficiently and safely.
Another type of tender-directed search we frequently use is sometimes called a “dock walk”. This sort of search creates rectangular search areas that are sometimes more efficient. In this search, a tender walks along a dock or shoreline tracking the speed and direction of the diver. The signalling process works the same way, with the tender directing the diver’s movements: stop, turn around, make the line taut, surface here, and so on. A dock walk creates a pattern like this.
Every tender-directed pattern has the same goals: 1) make sure the diver is safe, 2) make sure the search area is rigorously covered, without gaps, and 3) create documentation to efficiently conduct an extended multi-day search, if required. This is always a team effort. Tender directed diving is the basis for techniques that comprise the best-practices foundation California Recovery Divers uses for successful underwater recoveries.
