What is the most common type of ocean pollution?

Cigarette butts are the most common form of marine litter.

plastic pollution and littering

Explanation:

In an article, authors Jenny Griffin and Janaya Wilkins stated, “Plastics and polystyrene foam (Styrofoam) comprise 90% of all marine debris, with single-use food and beverage containers being one of the most common items found in ocean and coastal surveys.” This information shows that the biggest pollutant in the ocean, is one made by us humans, basically trash.