The Choice That Defines Your Vessel’s Towing Capability
When outfitting a tugboat for towing operations, the choice between a shark jaw and a towing hook is one of the most consequential equipment decisions you will make. Both systems connect your vessel to its tow — but they do so differently, serve different operational profiles, and carry different implications for safety, maintenance, and classification.
This article provides a clear, unbiased comparison to help naval architects, vessel operators, and procurement teams make the right choice for their specific application.
What Is a Shark Jaw?
A shark jaw is a hydraulically operated jaw assembly mounted on the tow deck or stern. It grips chain or wire rope between two opposing jaw plates, holding the towline securely without requiring the line to pass through or around any fixed fitting.
The key operational feature of a shark jaw is its positive mechanical grip: the jaws close under hydraulic pressure and remain closed until the operator deliberately opens them. Release is typically achieved via a quick-release handle or hydraulic valve, which can be operated remotely from the wheelhouse in modern installations.
Shark jaws are the standard towing device on AHTS vessels and are increasingly common on ocean-going tugs. They are designed for chain handling, although insert plate changes allow wire rope compatibility as well.
What Is a Towing Hook?
A towing hook is a fixed or semi-fixed deck fitting with a load-bearing hook and a latch mechanism. The towing wire or chain is looped over the hook and held by the latch. Release is typically achieved by a mechanical trip line or hydraulic cylinder that opens the latch, allowing the loop to fall free.
Towing hooks have been the standard towing device on harbour tugs for over a century. They are mechanically simple, low-maintenance, and well understood by crews worldwide. Their main limitation is that the latch mechanism relies on gravity and geometry to hold the load — conditions that can be compromised under shock loading or load reversal.
Key Differences
Safety Under Load
Shark jaw: Provides a positive grip that is independent of load direction. Whether the towing load is pulling fore, aft, or at an angle, the hydraulic pressure holding the jaws closed is not affected. Emergency release can be performed under full load from a remote location.
Towing hook: Latch mechanisms are designed for loads pulling in a specific direction. Load reversal — for example, when a tow surges forward and momentarily pushes against the tug — can cause the latch to trip unintentionally. This is a known failure mode, particularly on older hook designs. Deliberate release under high load can be difficult or dangerous if the mechanical trip mechanism is jammed or corroded.
Operation and Crew Handling
Shark jaw: Requires hydraulic power and trained operators familiar with the hydraulic circuit. Controls are typically simple (open/close valve), but the hydraulic system adds complexity to the vessel’s maintenance programme. Automated load-sensing and remote operation are available on modern systems.
Towing hook: Mechanically simple operation familiar to most tug crews. No hydraulic power required. Routine connection and disconnection is faster in calm conditions. However, connecting chain to a hook at sea in poor visibility or bad weather requires close physical access to the hook, which carries crew safety risks.
Capacity and Load Range
Shark jaw: Available in SWL ratings from approximately 75 MT to 700 MT+. Scales linearly with vessel size. The hydraulic clamping force can be adjusted to match the towline load, reducing jaw wear during light-load operations.
Towing hook: Generally limited to lower SWL ratings. Most harbour tug hooks are rated between 50 MT and 200 MT. High-capacity hook designs exist but are uncommon and the latch reliability issues noted above are more significant at higher loads.
Maintenance
Shark jaw: Requires periodic inspection of hydraulic cylinders, seals, jaw plates, and insert plates. Jaw inserts are wear items that require replacement after a defined number of operating cycles. Hydraulic fluid condition monitoring is essential.
Towing hook: Lower maintenance burden — primarily lubrication of the hinge pin and latch mechanism, and periodic load-test certification. The simplicity that makes hooks attractive in port also makes them easier to maintain with standard tug crew competencies.
Head-to-Head Comparison
| Feature | Shark Jaw | Towing Hook |
|---|---|---|
| Positive grip under load | Yes | No (latch-dependent) |
| Emergency release under full load | Yes (remote) | Difficult / risky |
| Load reversal resistance | Excellent | Poor |
| SWL range | 75–700+ MT | 50–200 MT typical |
| Wire rope compatibility | Yes (with inserts) | Yes |
| Chain compatibility | Optimised | Limited |
| Hydraulic system required | Yes | No |
| Crew training complexity | Moderate | Low |
| Maintenance complexity | Moderate | Low |
| Class approval (all major societies) | Yes | Yes |
| AHTS / offshore standard | Yes | No |
| Harbour tug tradition | Gaining adoption | Yes |
When to Choose a Shark Jaw
Choose a shark jaw when:
- Your vessel is engaged in AHTS, offshore anchor-handling, or deepwater towing — these operations are defined by chain handling and high dynamic loads that towing hooks cannot safely accommodate.
- You require remote quick-release capability from the wheelhouse or a safe standoff position.
- Your bollard pull exceeds 80 MT, placing you in SWL territory where reliable hook latches become increasingly difficult to source.
- You are handling anchor chain as a primary duty, not just wire towing.
- Your classification society’s towing notation explicitly requires a shark jaw (this is the case for AHTS notation under most societies’ offshore service rules).
- You want the option to upgrade to higher SWL in the future — shark jaw systems can often be re-rated with hydraulic system upgrades, whereas hooks typically cannot.
When to Choose a Towing Hook
Choose a towing hook when:
- Your vessel performs routine harbour towage with predictable, moderate loads and well-trained crews familiar with hook operations.
- Your bollard pull is below 60 MT and your towing operations are primarily short-scope wire towing in sheltered waters.
- Crew simplicity and low maintenance outweigh the safety advantages of a hydraulic jaw in your operational context.
- You are operating an existing vessel and retrofit cost is the primary constraint — hook replacement in an existing foundation is far cheaper than a shark jaw installation requiring new hydraulic infrastructure.
- Your operations are exclusively wire towing and your class society permits hook notation for your service.
Conclusion
For modern offshore and ocean-going towing operations, the shark jaw has become the dominant choice for sound engineering reasons: positive grip, high SWL availability, remote release capability, and classification society acceptance for the most demanding notations.
For harbour tugs performing conventional short-scope wire towing, a well-maintained towing hook remains a practical, cost-effective choice — provided loads remain within the hook’s certified rating and crew training includes awareness of latch failure modes.
If your vessel’s profile spans both environments, or if you are specifying new equipment for a vessel with multi-role ambitions, the shark jaw is the more future-proof investment.
To discuss which system is right for your vessel, visit the contact page and provide your bollard pull, operational profile, and class society. Our team will advise on the appropriate SharkJaw model or, where a towing hook is genuinely the better fit, we will tell you that too.