but all eyes remain on diana. it's now midday. 18 hours into the swim. >> i can't even swim. my muscles are going without oxygen. >> it's become clear that diana's condition is not improving. >> is it your lungs? >> dr. broder has to do something drastic. he grabs his stethoscope -- >> michael's coming out. >> -- and plunges into the water. first he tries the inhaler again. and then he returns to the boat and rigs this oxygen tank. he jumps back into the water desperate to get diana some air. >> i'm hyperventilating all the time. >> midnight, hour 28. diana has been swimming with bad