Abstract: A float member configured to float on and cover a fluid surface. The float member includes an elongated body having a top portion and a bottom portion defining a central longitudinal axis and a periphery portion. The periphery may have a substantially flat surface. The top portion extends upwardly from the periphery and the bottom portion extends downwardly from the periphery. A width of the body is substantially greater than a height of the body. In various aspects of the invention, the float member is configured to modify a transfer of evaporated fluid or energy therethrough. A method of forming a barrier using the float members and a system of for adjusting an evaporation rate of a fluid are further disclosed.