Cold water survivability modelling

HMCG have carefully considered and confirmed it is using the most appropriate model for survivability in cold water. This is because it adheres to the internationally set guidance from the IMO within IAMSAR (Volume 2) and aligns with guidance produced from the IMO’s Maritime Safety Committee. The model HMCG uses is supported by a SOP which draws upon the IAMSAR guidance to predict the time people can survive in cold water under a range of different scenarios. SOPs for people in the water group the collection of variables into who (e.g. name, age, physical condition, swimming ability and clothes), lifesaving equipment (e.g. use of life jackets), where (e.g. where they were last seen), when (e.g. when they were last seen), what (e.g. what happened to cause them to enter the water), how many and weather (e.g. sea state). For multiple people in the water, the information gathering is prioritised where required to understand how many people are in the water, if floatation devices have been deployed, has the location been identified and what is the on-scene weather, visibility, and water temperature. HMCG staff will also try to talk callers through the Float to Live advice, which guides people to control their breathing and float until help arrives. The US Coastguard is currently leading a project, working with other coastguard states, on a Probability of Survival Decision Aid (PSDA) on survivability in cold water. The aim is to gather sufficient data to establish whether a determination can be made to the IMO on whether the current IAMSAR guidance should be updated. Since 2022, HMCG has collaborated with the US Coastguard on this project and has shared all UK immersion data (such as age, sex, build, ability to swim, personal flotation devices are worn, time in the water) in support of this project. HMCG will continue to collaborate with this project and participate in any further activity related to the update of the IMO IAMSAR guidance.

The Department for Transport published its interim response to the Cranston Inquiry in July 2026, which included updates against this recommendation. This update noted that many of the recommendations - including this one - have been marked as complete but are necessarily based on an on-going approach, rather than having a single end point. The Department (DfT), the Maritime and Coastguard Agency (MCA), and His Majesty’s Coastguard (HMCG) are committed to on-going learning and improvement, and will regularly review processes and practices, learning from best practice, to ensure that they are fit to meet the evolving challenges of maritime search and rescue (SAR). Due to the operational and ongoing nature of these recommendations, the MCA has established an internal process of monitoring, verifying and reporting against recommendations that are its responsibility, noting that many recommendations require an on-going approach rather than reaching a single, fixed point.