Lipitor is a medication used to lower cholesterol levels in the blood. According to the drug patent watch website [1], Lipitor's active ingredient is atorvastatin calcium, which works by inhibiting an enzyme that is responsible for producing cholesterol in the liver. While there is no direct evidence to suggest that swimming can increase Lipitor's side effects, it is important to note that exposure to sunlight can increase the risk of muscle damage when taking Lipitor [2]. This muscle damage can cause pain, tenderness, weakness, and even kidney damage in severe cases [2]. A study published in the journal Circulation Research [3] found that exercise can increase the risk of muscle damage when taking statins, such as Lipitor. While swimming is a low-impact exercise, it is still important to take precautions when taking Lipitor. It is recommended to avoid prolonged exposure to sunlight, stay hydrated, and monitor any muscle pain or weakness when exercising while taking Lipitor. As always, it is important to consult with a healthcare professional before starting any exercise regimen while taking Lipitor.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.fda.gov/drugs/special-features/sun-and-your-medicine
[3] https://www.ahajournals.org/doi/full/10.1161/CIRCRESAHA.118.312782.