Which method is effective in controlling flooding?

Jettisoning equipment can be an effective method in controlling flooding during critical situations at sea because it involves removing excess weight from the vessel. By discarding heavy items, the vessel's overall stability can improve, reducing the risk of capsizing. This action may also help the ship to float higher in the water, potentially allowing it to manage the incoming water more effectively.

The other options, while relevant to flood situations in their own contexts, do not contribute positively to managing flooding directly. For instance, keeping watertight doors open would actually increase the risk of flooding rather than control it, as it allows water to spread more easily throughout the vessel. Securing all electrical power is a safety measure but does not address the flooding issue itself. Therefore, jettisoning equipment stands out as a practical approach to manage and mitigate the flooding conditions during a marine emergency.