Expect The Unexpected
From Openwaterpedia
noun - An understanding and experience among open water swimmers that the elements (e.g., wind, waves, currents, tides, marine life, water temperature, rain, lightening or fog), course (e.g., turn buoy placement, course layout, feeding station, start, finish structure, boating traffic, shoreline distance, official boat or kayak placement, escort boat fumes, mechanical boat failure), competition (pacing and positioning relative to other male, female and/or wetsuited swimmers or division separation) and one's own physical conditions (due to seasickness, lack of hydration or ill feeling to due food or drink mixtures) can present open water swimmers with unplanned surprises and special circumstances during an open water swimming competition or solo swim that requires swimmers to adapt and accommodate to the situation.
The swimmers expect the unexpected after the race director told them of the winds and rain that will hit the shoreline tomorrow.