( CNN ) -- Endurance swimmer Diana Nyad struggled through ocean swells , shoulder pain and asthma Monday as she attempted to become the first person to swim between Cuba and Florida without a shark cage , according to her team and a CNN staffer on a chase boat . Both the swells and the 61-year-old swimmer 's shoulder pain subsided somewhat and she was `` swimming strongly , '' her team said in a post to Facebook around noon ET . Follow Nyad on CNN 's tracker . The shoulder pain was `` down to an 8 '' following some `` therapeutic healing , '' the message said . The shoulder pain remained an issue around 2 p.m. , about 18 hours into the swim , said CNN staffer Matt Sloane -- who is following Nyad on a chase boat -- in a tweet . She is also having `` a little touch of asthma , '' he said . But he added that Nyad is `` still going very strong . '' Nyad in good spirits in 18th hour . The attempt to swim from Cuba to Florida is the second for the swimmer , who said at a news conference Sunday that she is fitter today than she was in 1978 , when she first attempted the crossing but was unable to finish . `` When I walk up on those shores of Florida , I want to prove to the AARP crowd that it 's not too late to go back and write that book or adopt that child , '' she said . She jumped into the water at 7:45 p.m . ET on Sunday and expects to swim for roughly 60 hours . She is stopping briefly each hour to eat . `` Nobody decides the swim is over except me , '' Nyad 's team quoted her on Twitter as saying . Wind , water , one woman 's drive . It took several months to gain permission for the swim from Cuban and U.S. authorities . Bureaucratic snags repeatedly threatened to call off the effort -- already called off in 2010 because of weather . Nyad has been training for the event for two years , swimming up to 12 hours a day . `` I 'm almost 62 years old and I 'm standing here at the prime of my life , '' she said Sunday as she prepared to dive into the water at Havana 's Marina Hemingway . `` I think this is the prime . When one reaches this age , you still have a body that 's strong but now you have a better mind . '' A team of more than 30 people is supporting Nyad as she attempts the crossing . She has 10 handlers to advise her as she swims , ocean kayakers towing devices to repel most sharks and divers and safety officers trained to distract those that are n't turned away . A doctor is also on hand .
NEW : Diana Nyad : `` Nobody decides the swim is over except me '' She struggles through ocean swells , shoulder pain and asthma . She is attempting the second crossing from Cuba to Cuba without a shark cage . Nyad began Sunday 60 hours and hopes to swim the 103-mile span in night .