On hot, humid days, you might jump into water to cool down, but for the tiny mangrove rivulus fish, cooling down means jumping out of water, according to a new study from the University of Guelph.In the study published today in the journal Biology Letters, the researchers describe how these fish air-chill themselves on solid ground in order to drop their body temperatures. The researchers also found that fish exposed to higher temperatures for a week tolerated warmer water better.The fish jump out of the water to escape rising temperatures, said integrative biology professor Pat Wright, senior author of the study.