After swimming in the ocean for several hours, the swimmers noticed that their fingers appeared to be very wrinkled or shriveled up. this is an indication that seawater is relative to the fluid in cells.

The answer is hypertonic. In osmosis, water molecules move from a hypotonic solution to the hypertonic solution, through a semipermeable membrane. This occurs until both solutions become isotonic relative to each other.  In osmosis, only the movement of water molecules occurs since the ions are large enough to pass through the pores of the semipermeable membrane, in this case, the cell membrane. Due to loss of water in the process of osmosis, the cells in the fingers of the swimmers shrunk hence looked shriveled.