Dead zones—areas in the ocean where oxygen levels are so low that marine life cannot survive—are expanding and becoming more common. These zones are primarily caused by human activities, such as agricultural runoff and wastewater discharge, which introduce excessive nutrients into water systems. These nutrients, mainly phosphorus and nitrogen, lead to a process called eutrophication, where algae grow rapidly. When this algae dies and decomposes, it consumes oxygen, creating hypoxic or anoxic conditions that are deadly to marine organisms. The Lincoln Memorial basin, an artificial water feature in Washington, D.C., faced a similar issue before the 250th anniversary celebrations of the American Declaration of Independence. Despite a thorough cleaning, the water turned green due to an overgrowth of algae. To address this, engineers installed an ozone nanobubble generator, a technology that produces extremely small gas bubbles from ozone. Unlike regular bubbles, which rise and burst quickly, these nanobubbles remain suspended in the water for much longer. Ozone is a strong oxidizing agent that breaks down algae and organic matter, helping to restore the water's clarity. However, the success of such treatments depends on the specific characteristics of the water body. The Lincoln Memorial basin is artificial, shallow, and has a hard bottom, making it easier to manage than a natural lake. The water must be continuously circulated, and the treatment must be maintained over time. Ozone, while effective in this setting, is not selective—it attacks all organisms, which could be problematic in natural ecosystems where preserving biodiversity is a priority. The broader issue of oxygen depletion in the world’s oceans is growing more severe, especially near coasts, and is linked to climate change. A report by the International Union for Conservation of Nature (IUCN) highlights the alarming drop in oxygen levels, which threatens marine life and the people who depend on it. In natural environments, the cycle of nutrient release and algae growth can create a self-sustaining loop that leads to dead zones. Addressing this problem requires more than just adding oxygen to the water; it involves delivering it precisely to the sediment layer where these processes occur. Technologies such as volume nanobubbles and interface oxygen nanobubbles are being explored to improve oxygenation. While volume nanobubbles work well in controlled environments like aquaculture and wastewater treatment, they require continuous mechanical circulation and can be energy-intensive. Interface oxygen nanobubbles, on the other hand, use porous materials to deliver oxygen directly to the sediment, reducing energy use and ecological disruption. However, these solutions are still complex and costly, especially in large, vulnerable bodies of water like the Baltic Sea, where natural conditions make oxygenation even more challenging. Ultimately, no technology can fully counteract the effects of nutrient pollution if the root causes—such as fertilizer runoff and wastewater discharge—are not addressed. Experts emphasize that a comprehensive strategy must include removing nutrients from the water, stabilizing sediments, and carefully oxygenating the bottom layers. While artificial solutions may provide temporary relief, the long-term answer lies in sustainable practices that prevent the problem from worsening in the first place.