In situ observations of habitat use by southern cavefish (Typhlichthys subterraneus) in a Missouri, U.S.A. spring suggest that groundwater discharge and that zones of substrate which have large interstitial spaces that fish can enter may be important components of the species habitat. Such substrates may also facilitate smallscale dispersal. In addition, we document the first recorded case of gas bubble disease in a laboratory-held specimen of this species. Cavefish may be particularly susceptible to this malady, and the conditions under which it occurred are important to avoid should captive maintenance or propagation of this or related species be attempted.