**Core Concept**
Freshwater swimming can cause a serious condition known as Acute Respiratory Distress Syndrome (ARDS) due to the rapid dilution of sodium ions in the blood, leading to a shift in water into the cells, causing hemolysis and subsequent release of potassium ions, which can be fatal if not treated promptly.

**Why the Correct Answer is Right**
The rapid dilution of sodium ions in the freshwater causes an osmotic shift of water into the cells, leading to hemolysis and the release of potassium ions. This can cause a severe drop in blood sodium levels (hyponatremia), leading to cerebral edema and potentially fatal outcomes if not treated promptly. The body's inability to regulate the influx of water into the cells is due to the lack of sodium ions to maintain the osmotic balance.

**Why Each Wrong Option is Incorrect**
**Option A:** This is not a known consequence of freshwater swimming.
**Option B:** While this is a potential consequence of drowning, it is not specifically related to freshwater swimming.
**Option C:** This is a potential consequence of saltwater drowning, not freshwater.

**Clinical Pearl / High-Yield Fact**
Remember the "Fencl-Nephrology" formula to estimate the severity of hyponatremia: 1 mmol/L decrease in sodium levels per 1% increase in body water. This can help you estimate the severity of hyponatremia and guide treatment.

**Correct Answer:** D.