Observations of pyroclast and hydroclast production during subaqueous volcanism at depths >1 km have become common in the literature, despite early predictions that such activity would be pressure-limited. Direct near-vent observations of active submarine eruptions (first at NW Rota-1 and West Mata in the 2000s, e.g., Murch et al., EPSL 2022) revealed multiple volcaniclastic generation modes: in-conduit magmatic fragmentation, external water-induced fragmentation at the vent, and cooling-contraction fragmentation of lava injected molten into the water column. Follow-up studies of stratigraphy and edifice morphology at these and other sites indicate that such processes are widespread and contribute significantly to volcanic structure, hydrology, and ecology. We report here on several substantial primary and secondary pyroclastic deposits from recent eruptions in Tonga’s NE Lau Basin (mainly at West Mata and Tafu volcanoes), as well as undated but likely late Holocene deposits in nearby areas, which display volumetrically significant volcaniclastic output during mafic submarine eruptions as thick vent-proximal and thinner, broad distal deposits with diverse particle morphologies. Explosive fragmentation under these conditions can also produce varied landforms and promote slope instability. Observations from 7 NSF-, NOAA-, and SOI-sponsored cruises (2009–2018), using ROVs and AUVs, reveal both new and older tephra blankets, periodic downslope transport, and distal ripple-structured deposits. Decreasing grain size and thickness generally with distance from the vent location, imply primary pyroclast deposition as well as secondary reworking; in other cases (especially at deep sites), sand-sized and smaller grained-deposits show evidence for transport bedforms (ripples) and post-depositional reworking (sinkholes). At West Mata (2016–17 eruptions; Chadwick et al. 2019) and post-2011 Tafu (Rubin et al., AGU 2020) events, pyroclastic layers up to 1–2 m thick buried lava flows, indicating explosive final phases. Sampling these deposits for grain size/shape characterization is challenging due to coarse fragments near vents and fine particles distally, but can be done using push cores with catchers and scoop bags for basic grain size and shape analysis