We report information on morphological variation and behavior of the recently described watersnake Helicops boitata, previously known strictly from the holotype. Our data come from five new specimens fortuitously found in a private area near the type locality, in the Brazilian Pantanal wetlands. The expanded sample revealed polymorphism in at least two scalation features assumed as diagnostic of the species (i.e., undivided condition of the cloacal plate and nasal scales) and confirmed the uniqueness of the ventral color pattern, as well as the divided condition of the foremost ventral shields. Besides, as reported for the holotype, three individuals collected alive also exhibited harmless behavior when handled, a rather unusual feature among snakes of the genus Helicops. Other new behavioral observations include a mostly nocturnal activity (in contrast with the previous data) and the ability to dig galleries in the soft substrate when attempting to escape. The finding of five individuals very close to each other suggest aggregations in habitats retaining humidity in the dry season of the Pantanal. Low abundance rates and possible habitat restrictions might render Helicops boitata particularly susceptible to seasonal fire episodes that consume large extensions of the wetlands, including dry swamps in which aquatic reptiles find refuge during the seasonal droughts.

We collected the new specimens of Helicops boitata and deposited them in the Coleção Herpetológica do Instituto de Biociências da Universidade Federal de Mato Grosso (UFMT-R) (see Sabaj 2020). Two snakes freshly killed by the bulldozer were collected on 15 (UFMT-R 12520) and 16 (UFMT-R 12521) October of 2019. UFMT-R 12520 was found by LVSC belly up (exposing its unique ventral pattern) on the bare surface of the soil. UFMT-R 12521 was found the next day, dead and deeply injured, together with many individuals of Helicops leopardinus (Schlegel, 1837) and other three individuals of H. boitata, alive and unharmed (UFMT-R 12504, 12505 and 12506)

When arrived from the field, the alive specimens remained provisionally accommodated in a semi-aquatic terrarium to be euthanized after three days. The terrarium cube (101 cm length, 51 cm width, 61 cm height, Fig. 1) contained quartzitic sand as the main substrate and a fragment of peat soil obtained in the collection site with the snakes. The sand inside the system exhibited an elevated area of 23 cm high at one of the extremities of the cube representing a permanently dry spot. The snakes (entangled in the peat fragment, exactly as found in the field) were accommodated in this area of the terrarium. The system contained nearly 90 L of water attaining a maximum level of 15 cm, as well as macrophyte plants [Pistia stratiotes (Araceae) and Eichhornia crassipes (Pontederiaceae)] floating on the water surface. We attached a clamp black light lamp to the glass wall of the cube to provide proper illumination during nocturnal observations. From October 17^th and 19^th, two of us (GVA and SSW) observed the specimens in shifts from 6:00 AM to 9:00 PM, reporting any events of activity displayed by any of the three individuals. At 6:00 PM, we turned off the lights of the lab and turned on the black light lamp, keeping nocturnal observations until 9:00 PM, when observations were interrupted until the next morning.