In the marine environment, anthropogenic pressures on resources and non-anthropogenic causes may create harmful conditions that affect human society. Harmful algal blooms and habitat destruction are examples, which pose serious human-health threats and severely affect numerous industries, causing annual economic losses in the tens of millions of euros, in the form of reduced sales, diminished tourist activity and unemployment. A widely adopted, scientific way to assess the environmental status of water bodies is by measuring their optical properties (as indicators of, e.g., sewage impact, dissolved organic matter, sediment load or gross biological activity). The Citclops project aims to develop systems to retrieve and use data on seawater colour, transparency and fluorescence, using low-cost sensors combined with contextual information (e.g., georeferencing) and a community-based Internet platform, taking into account existing experiences (e.g., Secchi Dip-In, Coastwatch Europe and Oil Reporter). Simple and fast methods to establish the optical properties of seawater will be developed and used: e.g., the colour through Forel-Ule observations, and transparency through a variant of the Secchi disc. People will be able to acquire data taking photographs of the sea surface on ferries or other vessels, at the open sea or from the beach. Wearable digital cameras for aquatic activities with extended sensing systems are also proposed as alternative resources for crowdsourcing data. Data are automatically uploaded through a specific service or application (such as Google+ Instant Upload), archived remotely and processed, and resulting information is accessed through a webpage or a mobile application by end users. These are: policy makers (e.g., local administrations), which will be able to use the information to improve the management of the coastal zone; and citizens, who will be able to maximize their experience in activities in which water quality has a role.