At the request of the United States government and BP, research scientists and technicians from the Centre for Offshore Oil Gas and Energy Research (COOGER), Fisheries and Oceans Canada (DFO) conducted at-sea monitoring operations with other scientific experts on board vessels R/V Brooks McCall and R/V Ocean Veritas. From May 8 through August 24, 2010 the DFO COOGER team maintained a continuous monitoring program that recovered a total of 3197 unique water samples from 404 stations at depths down to 2000 m for analysis of dispersant effectiveness by characterizing oil droplet size and UV-fluorescence. This collection of data is organized into nine database tables which include all data used by COOGER to conduct analyses. These data include: 1.LISST data for in situ deployments; 2.discrete LISST data collected aboard R/V Brooks McCall and R/V Ocean Veritas; 3.UV Fluorescence data collected aboard the R/V Brooks McCall and R/V Ocean Veritas; 4.Hydrocarbon chemistry data; 5.CTD trace data; 6.CTD trace data matched to Niskin bottles; 7.R/V Brooks McCall and R/V Ocean Veritas sampling station data (date, depth, location, and distance from wellhead); and 8.Wellhead data including daily oil flow and recovery, and dispersant application data.