The reservoir itself has designated swim areas that see plenty of tourist traffic, especially on weekends. For a genuinely quieter swim, locals tend to look slightly further afield, in the surrounding countryside rather than right in town.
Rural streams and swimming holes nearby
The broader area around Guatapé and neighboring El Peñol has smaller natural streams and swimming spots used by rural families rather than tour groups — these are generally unmarked and known through word of mouth rather than signposted, so a local recommendation or a guide who knows the specific spot is genuinely useful here rather than optional.
Why these stay quiet
Unlike the reservoir's main swim areas, these rural spots aren't set up with vendor infrastructure, parking, or safety monitoring — part of their appeal for locals, but also a reason to treat them with more caution than a designated swim area, and ideally not go alone or without knowing the specific access point.
A simpler alternative: early reservoir swimming
If venturing further out isn't practical for your trip, an easier version of the same idea is simply using the reservoir's swim areas early in the morning, before the weekend crowds and boat traffic pick up — not a secret, but a real improvement over midday conditions.
A word on safety
Water conditions and access at unmarked rural spots can vary and aren't professionally monitored the way tourist swim areas are — if you're pursuing this, going with someone who genuinely knows the specific location, rather than searching blind, is the smart move.