Water in hot springs can cause severe or fatal burns, and scalding water underlies most of the thin, breakable crust around hot springs. More than 20 people have died from burns suffered after they entered or fell into one of Yellowstone's hot springs.

Falling into a geyser or a hydrothermal pool at Yellowstone is almost certainly fatal and catastrophic for the human body. These pools are not just hot; many are at or near boiling temperatures (199∘F or 93∘C at Yellowstone's altitude). Beyond the heat, many springs are highly acidic—some with a pH similar to battery acid—due to microorganisms that break down surrounding rock into sulfuric acid. If a person falls in, the boiling water causes immediate third-degree burns, and the intense heat can lead to rapid thermal shock. In extreme cases, the combination of high heat and high acidity can actually dissolve a body completely, including bones, within less than 24 hours. This occurred in a tragic 2016 incident where no remains could be recovered. The park's boardwalks and warning signs are strictly enforced because the "crust" around these pools is often deceptively thin and can collapse under the weight of a person, plunging them into the superheated, caustic reservoir below.