Marine transportation safety investigation M23A0169

The occurrence

On 18 June 2023, the submersible Titan, with 5 people on board, was descending to the wreck of the Royal Mail Ship Titanic, located 372 nautical miles south-southeast of Cape Race, Newfoundland and Labrador. The Titan was owned by the U.S.-based company OceanGate.The Titan was owned by OceanGate, Inc.., a corporation organized under the laws of the State of Washington in the United States; it was operated by its wholly owned subsidiary, OceanGate Expeditions, Ltd, a Bahamas entity. The Titan was being supported by a Canadian cargo vessel, the Polar Prince, which was being used to tow the Titan to and from dive locations, as well as providing a base for OceanGate’s operations. During the Titan’s descent, an OceanGate surface support team aboard the Polar Prince was tracking the Titan and maintaining communication. Approximately 1 hour and 45 minutes after the Titan began its descent, the surface support team lost all contact with it. A search and rescue operation was initiated later that evening. On 22 June, the U.S. Coast Guard confirmed that the wreckage of the Titan had been found on the ocean floor near the Titanic. There were no survivors.

The Titan’s pressure hull consisted of a carbon fibre cylinder that was capped at either end by titanium domes. The use of carbon fibre in a pressure hull for a human-occupied submersible intended for deep-ocean diving is novel; submersibles used for deep-ocean diving are typically constructed of steel or titanium. As well, the pressure hull is typically spherical, not cylindrical, because this is the best shape for resisting external pressure and allowing even distribution of stresses.

The investigation determined that the as-built properties of the Titan’s carbon fibre cylinder were never validated to ensure they met the theoretical values used in the design process and that the construction and testing of the Titan did not follow standard engineering practices. As a result, OceanGate did not know for how long the Titan’s pressure hull would remain structurally intact when used repeatedly for dives to the depth of the Titanic.

In an attempt to mitigate this problem, OceanGate had developed 2 systems to monitor the integrity of the pressure hull: a strain monitoring system and an acoustic monitoring system. The strain monitoring system provided data for post-dive analysis to identify potential problems with the pressure hull that could lead to failure on a subsequent dive. However, analysis of the strain data by OceanGate was inconsistent and did not result in the pressure hull being removed from service before its failure. The acoustic emission monitoring system was being relied on to provide enough advance warning for the submersible to surface in the event of an impending hull failure. However, this system had not been tested to demonstrate that it would consistently provide enough advance warning, and it did not function as intended during the occurrence.

Analysis by the TSB Laboratory determined that the reduced compressive strength of the Titan’s carbon fibre cylinder, as well as defects that were potentially introduced during manufacturing, operations, storage, and transport of the Titan, likely led the cylinder to fail progressively, due to damage accumulating during each dive cycle, until it imploded. 

The investigation found that risk management at OceanGate was hindered by the structure and composition of the company as well as by the influence of power dynamics and social and psychological factors. As a result, OceanGate did not identify and mitigate key risks associated with the structural integrity of the Titan. Also, the investigation looked at issues relating to oversight of submersible operations, emergency response preparedness for submersibles, and safety management as it relates to groups working on a vessel.

The investigation identified safety deficiencies related to oversight and standards that led the Board to issue 6 recommendations.

Canada’s approach to regulatory oversight

Under the Canada Shipping Act, 2001 (CSA 2001), Transport Canada (TC) is responsible for marine safety, security, and environmental protection in relation to Canadian vessels and foreign vessels operating in Canadian waters. Regulatory oversight from TC provides independent verification of the safe operation and regulatory compliance of these vessels through inspections either for mandatory certification where required, or compliance with regulations. 

How TC identifies vessels and provides oversight depends on whether a vessel is Canadian or foreign-registered and on its size. For Canadian commercial vessels that do not require a certificate to operate and foreign vessels under international tonnage thresholds (500 GT), oversight consists of “risk-based inspections” or TC visits; TC may visit such vessels if they receive reports that raise concerns or may act based on their own observations. Although TC was aware that the Titan was operating from St. John’s and that it was supported by Canadian vessels, TC was unaware that the Titan was not registered with any flag state. The Titan did not receive any oversight from TC.

This situation is not unique; in fact, in Canada, it is relatively common for vessels to receive no oversight from TC. The investigation found that the lack of regulatory oversight to identify safety deficiencies resulted in increased risk to those involved in the Titan’s operations. Since 2015, the TSB determined that a similar lack of regulatory oversight was a factor in a number of occurrences involving uncertified and unregistered fishing vesselsTSB marine transportation safety investigation reports M21A0315, M20A0160, M19A0090, and M16A0327. and uncertified tugs.TSB marine transportation safety investigation reports M21P0030, M20P0230, M17P0244, and M15P0037. Given that uncertified vessels, such as the Titan, are often not subject to any regulatory oversight in Canada, the Board recommends that

The Board also recommends that 

Information sharing between Transport Canada and other government departments 

Given the nature of marine operations, vessels and vessel owners and operators interact with government entities outside of TC, such as the Canadian Border Services Agency (CBSA), Fisheries and Oceans Canada (DFO), provincial authorities, and port authorities. A number of Canadian government departments, including DFO, interacted with OceanGate from 2019 up until the time of the occurrence.

The more information that TC has about a vessel’s operation, the greater the ability to assess risk and determine the appropriate level of oversight. Previous investigationsTSB Marine Transportation Safety Investigation Report M20A0160. have identified issues with information sharing between TC and other government departments. However, TC has no processes to obtain and use this information. Some progress is being made: in response to the Board’s recommendationTSB Recommendation M22-01, Requirement for Transport Canada vessel registration prior to Fisheries and Oceans Canada issuance of fishing licence, at https://www.tsb.gc.ca/eng/recommandations-recommendations/marine/2022/rec-m2201.html (last accessed on 20 May 2026). that the Department of Fisheries and Oceans require that any Canadian vessel that is used commercially to harvest marine resources have a current and accurate TC registration, DFO is working more closely with TC and the number of vessels registered with TC and licensed by DFO has increased. 

The investigation found that there is limited information-sharing between TC and other government departments, which results in TC missing opportunities to access information that could be useful in assessing risk in commercial vessel operations and determining the appropriate level of oversight. Such information from other government departments can enable TC to act and evaluate a vessel’s operation from a Canadian port and within Canadian waters. Therefore, the Board recommends that 

Oversight of submersibles

A submersible operator can obtain oversight for their submersible by classifying the submersible with a classification society or by registering the submersible with a flag state that provides oversight of submersibles. Some countries, including the Bahamas, the Cayman Islands, and Japan, require submersibles to be classified with a classification society. Other countries, have regulatory frameworks that cover the operation of submersibles. Some countries, such as Canada, have limited or no regulations in place. 

The International Maritime Organization (IMO) has provided guidelines for the design, construction, and operation of submersibles that carry passengers (MSC Circular 981).International Maritime Organization, MSC Circular 981 – Guidelines for the Design, Construction and Operation of Passenger Submersible Craft (29 January 2001). However, this guidance is not incorporated into any international conventions or codes. As a result, it is only binding at the national level where member states have incorporated it into domestic regulations.  Without a mandatory international standard for submersibles, oversight of submersible operations relies largely on individual flag state requirements, and safety depends largely on voluntary action from owners and operators, increasing the risk to people, vessels, and the environment. TC represents Canada as a member state at the IMO and can advocate for safety-related changes. Therefore, the Board recommends that

In Canada, submersibles are included in the definition of a vessel under the CSA 2001 and are therefore subject to the same regulatory oversight as other vessels. However, there are no comprehensive or specific regulations in Canada that govern the construction or the operation of human-occupied submersibles, although there are regulations regarding crewing.

In 2004, concerns were raised about passenger submersible operations in the Haliburton Forest and Wildlife Reserve, Haliburton, Ontario. In response, TC created a policy on domestic passenger submersibles that came into effect in 2005.Transport Canada, Tier 1 – Policy: Passenger Submersible Craft, 2005. The objective of the policy was to implement the IMO’s guidelines for passenger submersibles (MSC/Circ. 981). In April 2026, TC released Ship Safety Bulletin (SSB) 03/2026: Requirements for passenger submersibles operating in Canadian waters. The SSB identifies an approach to the department’s oversight of submersibles, using instruments, norms, and standards that existed at the time of the Titan’s operation, and adds reporting requirements for dive operations.

The implementation of MSC Circ. 981 through the TC policy on passenger submersibles and the publication of new and existing requirements in SSB 03/2026 are both steps in the right direction. However, SSBs and policies are intended to guide behaviour and are not enforceable. It is unclear if these steps will mitigate the risk associated with the operation of a vessel such as the Titan in the future. Without mandatory oversight of similar operations, covering all human-occupied submersibles, the underlying risk remains. Therefore, the Board recommends that

Safety management system practices for one or more groups working on a vessel 

Certain types of operations can result in 1 or more groups working on board a vessel. In operations where 1 or more groups are working on board, there will be interactions between the vessel’s SMS and the various systems used by other groups to manage safety. The company that operated the Polar Prince, Horizon Maritime Services Ltd., had an emergency response plan that noted that specific customer requirements for emergency response should be addressed in a bridging document and a joint emergency response plan. Typically, bridging documents are implemented to clarify how operations, including emergency response, will be coordinated and how safety will be managed. Bridging documents are common in certain industries, such as the oil and gas industry.The International Association of Oil & Gas Producers has guidance on bridging documents (https://www.iogp.org/bookstore/product/guide-to-preparing-hse-plans-and-bridging-documents-supplement-to-report-423/, last accessed on 12 May 2026). The Canadian oil and gas industry, in general, follows the guidance set out by the International Association of Oil & Gas Producers. In Norway and the Netherlands, there are requirements for bridging documents in the offshore oil and gas industry. For operations like those being undertaken by the Polar Prince and OceanGate, there is no external requirement for a bridging document to be developed.

When 1 or more groups work on board a vessel without comprehensive guidance from a bridging document to integrate safety management between their operations and those of the vessel, there is a risk that operations will be conducted without the necessary safeguards. The Board therefore recommends that

Safety communication