From sweeping a seafloor swath the size of Manhattan in minutes to zooming in on a single china plate 4 km down, today’s wreck hunters rely on an integrated toolbox of sonar sensors and remotely operated vehicles (ROVs).

Quick definition (TL;DR)

Side-scan and multibeam sonar fire sound pulses that bounce off the seabed; ROVs (remote-controlled submersibles) and AUVs (autonomous drones) then “ground-truth” promising targets with HD cameras and manipulators. oceanexplorer.noaa.gov

1. The modern toolkit at a glance

Tool	What it delivers	Typical range	Best for
Side-scan sonar	Photo-like “shadow” images of objects	50–600 m swath	Detecting hull shapes, debris fields
Multibeam sonar	Bathymetric 3-D terrain map	100–7,000 m depth	Locating anomalies, creating mosaics
Magnetometer	Measures magnetic disturbances	≈ 30 m radius	Iron/steel wrecks in sediment
Sub-bottom profiler	Penetrates mud/sand layers	Up to 50 m below seabed	Buried wooden wrecks
ROV	Live video, manipulation	Tethered to ship, 1–6 km depth	Close-up ID, small artefact recovery
AUV	Autonomous survey, long endurance	24–96 h missions	Wide-area mapping beyond human reach

(See our interactive shipwreck map for real-world sonar tracks and depths.)

2. Sonar 101: painting the seabed with sound

A. Side-scan sonar

A towfish dragged behind the survey vessel emits fan-shaped sound beams; objects cast acoustic “shadows” that reveal outlines of masts, cannons or cargo boxes. oceanexplorer.noaa.gov

B. Multibeam sonar

Mounted on the ship’s hull, an array of transmitters fires hundreds of beams downward to produce a colour-coded 3-D model. On a single pass it can map a lane several kilometres wide, flagging unnatural bumps for closer inspection. oceanexplorer.noaa.gov

Workflow tip: Crews often run a broad multibeam grid first, then switch to side-scan for high-resolution images of the anomalies. oceanexplorer.noaa.gov

3. Eyes-on tech: ROVs, drones & crawlers

Vehicle	Depth rating	Notable missions
VideoRay micro-ROV	305 m	USS Arizona, Lusitania site VideoRay
ROV Jason (WHOI)	6,500 m	Recovery of ROV Hercules & Argus after Mediterranean snag Woods Hole Oceanographic Institution
NOAA 4K ROV system	1,000 m	2025 Lake Ontario National Marine Sanctuary dives sanctuaries.noaa.gov
HUGIN AUV	4,500 m	Norway’s 400-m-deep medieval wreck, 2024 Live Science

Unlike tethered ROVs, AUVs fly pre-programmed lawn-mower patterns, collecting multibeam and side-scan data for days without a mothership—ideal for under-ice or deep-ocean searches.

4. A four-step discovery workflow

1. Desktop research – Archive charts, survivor accounts, drift models.
2. Broad-area multibeam pass – Builds high-resolution bathymetry.
3. Targeted side-scan & magnetometer lines – Confirms man-made structure.
4. ROV/AUV ground-truth – HD video, laser scaling, sampling.

(New to heritage rules? Review Shipwreck 101 #1 – What Counts as a Shipwreck before touching anything.)

5. Case studies

• Lake Ontario, 2025: NOAA team used multibeam + a compact ROV to livestream three 19th-century schooners to YouTube classrooms. sanctuaries.noaa.gov
• Norway’s Mjøsa Lake, 2024: An AUV mapping mission revealed a perfectly preserved 700-year-old clinker-built vessel at 400 m—too deep for divers, now monitored by ROV. Live Science
• Mediterranean, 2021: WHOI’s Jason rescued two stranded vehicles while surveying Phoenician wrecks, proving redundancy planning pays. Woods Hole Oceanographic Institution

6. Costs & permissions

Item	Hobbyist	Academic / pro
Fish-finder side-scan kit	£1.5–3 k	–
Professional towfish + topside	–	£30–200 k
Inspection-class ROV	£6–20 k	£50–300 k (work-class)
Multibeam lease (per month)	–	£50 k+ incl. crew

Before splashing any tech, you’ll still need permits under your flag State’s heritage or salvage laws—see our upcoming Salvage Law 101 post.