AbstractA large variety of biotic and abiotic processes take place close to the sediment-water interface, causing and being affected byphysical, biological and chemical gradients below and above this transition zone. Adequate sampling of this environment isessential for a comprehensive understanding of the complex sea floor ecological systems. The multi-horizon bottom watersampler (BoWaSnapper) presented here was developed for instantaneous sampling of the transition zone above the seafloor andcan be deployed in all types of water bodies from coastal seas to full ocean depth (6000 m). The intention was to construct aninstrument that could bridge the gap between the sampling of the bottom water column by conventional CTD rosette andsediment sampling gear such as a multiple corer.The BoWaSnapper was designed to be operated on any research ship?s wire and allows time-efficient high-resolutionsampling of bottom water. The bottommost 2 m are sampled with six vertically adjustable bottles. Prior to closure, the bottlesare aligned with the bottom current by means of a vane and flushed by bottom water for several minutes. This ensures thatparticles dispersed upon the touch-down of the BoWaSnapper are flushed away. An electronic mechanism, activated by abottom switch, initiates bottle closure after a delay pre-selected by the user. As illustrated by several examples, the transparentbottles (6 L volume each) allow the determination of particle concentrations as well as the analysis of solutes such as nutrients,dissolved gases, and natural radiotracers. Although the sampler is universally suitable for seafloor environments, its specialdomain is characterised by steep geochemical gradients such as cold vents and submarine groundwater discharge.Keywords: Bottom water; Benthic boundary layer; Water samplers; Vertical distribution; Solutes; Particle concentration