Which step should normally be taken first by those who have boarded a liferaft in an emergency?

The first step that should be taken by individuals who have boarded a liferaft in an emergency is to take anti seasickness pills, if available. This is crucial because seasickness can severely impair an individual's ability to think clearly and respond effectively to the situation at hand. If crew members become nauseated, they may be unable to actively participate in making decisions, steering the liferaft, or using emergency equipment.

Administering anti seasickness medication at the outset helps to minimize discomfort and allows survivors to remain alert and engaged in the emergency response. This proactive measure also helps facilitate better communication and cooperation among those on board, which is vital in crisis situations when every member's input and actions can be critical for survival.

The other actions, while important, can be addressed after addressing potential seasickness. For instance, checking pyrotechnic supplies, rationing food and water, and determining position and closest point of land are all sound survival strategies but rely on the crew's capability to perform these tasks effectively. If the crew is incapacitated by seasickness, these essential steps may be delayed or inadequately executed.