The growing concern of the world community to face the emerging planetary crises demands overcoming several complex scientific, management, and governance challenges. Marine litter exemplifies such a wicked problem, with different sources, paths, sinks, effects, and solutions, and has become a priority in the international agenda. The Sustainable Development Goal 14 (life below water) of the United Nations 2030 Agenda for Sustainable Development and the United Nations Decade of Ocean Science for Sustainable Development (2021-2030) are committed to a clean, healthy, and resilient ocean. Combating marine litter requires science-driven, holistic, and diversified approaches considering the whole life cycle of human-produced and used materials, as stated in Resolution 5/14 of the United Nations Environment Assembly, to develop an international legally binding instrument on plastic pollution, including in the marine environment. Understanding the land- and sea-based sources and the fates of plastics, including their transboundary movements and spatial and temporal patterns, unveiling the effects on marine ecosystems and human well-being, supporting solutions, and evaluating the policy effectiveness requires coordinated efforts towards harmonization of monitoring and assessment of plastic pollution. The strategies for preventing plastic pollution, including the development and efficacy of innovative recycling, alternative materials, biodegradable materials, and clean-up technologies, also depend on scientifically sound criteria considering the costs of the alternative materials. These are examples of encrypted messages in a plastic bottle that still need to be objectively unveiled by science and faced by society to produce the ocean we need for the future we want.