Legend claims every year a mermaid living in the laguna takes one man. The inability of certain Peruvians to swim seems a more likely explanation of the yearly drownings. Other people speculate that the cause of the frequent drownings is swimmers muscles cramp when the warm water on the top of the oasis mixes with cooler water below.
Taxis leave Huacachina at all hours of the day and night. If you plan on leaving the area in order to go to Lima, ask the driver to take you to the bus station for Soyuz (32 soles for the "VIP" bus) or Cruz del Sur (more expensive but nicer). If you are going to Arequipa, options are Cruz del Sur and Cial (the budget option).
Peru Hop a new service offer direct buses daily between Huacachina and Lima, Nasca, Arequipa or Paracas rather than into the nearby city of Ica.