A plastic envelope of 0.004 inch thick polyethylene is suggested as a substitute for drift bottles. The return card is sealed hermetically in the envelope, thus forming an inexpensive, compact and convenient means for studying surface currents by conventional drift bottle technique. Tests indicate that "drift cards" actually indicate surface flows and are not at the complete mercy of the winds.
Olson, F. C.. 1951. "A plastic envelope substitute for drift bootles." Journal of Marine Research 10, (2). https://elischolar.library.yale.edu/journal_of_marine_research/745