A few unqualified points, but you can trust me on these.
Floaters can be so bad in bright sunlight that driving a car is impossible. In the evening they could be almost insignificant due to the lens being much bigger and the shadows not so contrasted. It is likely that the sufferer will find that they disappear almost completely within a few days/weeks.
Cut back on hard booze, and get good UV filters.
Sudden onset can be indicative of many things including Posterior Vitreous Detachment. In this case a perfectly clear eye can be filled with thick dark floaters within seconds. A bright yellow moon-like crescent--flashing to one side--is another clue of PVD.
Obviously, any sudden eye defect needs the attention of a specialist. Many hospitals in the UK have an emergency clinic.