With 7000 M_ȯ inside a radius of 0.3 pc, DR21(OH) is the most massive nearby sub-parsec size scale clump at less than 3 kpc from Sun (Motte et al. 2007, A&A 476, 1243). With a size similar to the Orion Nebula Cluster (ONC), it has the potential to form a 3 times more massive cluster than the ONC. It already contains a hot core/HCHII region (Araya et al. 2009, ApJ 698, 1321), as well as at least 2 class 0 like massive protostars (Bontemps et al. 2010, A&A 524, 18). It is also the possible location of the impact of a flow of material from a large scale filament detected in CS/N2H+ by Schneider et al. (2010, A&A 520, 49) falling on the clump. Using the IRAM PdBI we have resolved out the complex structure of the region both in the dust continuum and in several molecular lines (N2H+, CH3CN, H2CO, HC3N) and have found that it is actually governed by supersonic flows (see Csengeri et al. 2011, A&A 527, 135). Using the HIFI instrument, and as part of the WISH guaranteed time key program, we have observed DR21(OH) in more than 10 transitions of water and isotopologues which have all been detected with complex line profiles which are tracing the kinematics in the inner regions of the proto-cluster. From these high resolution observations and new water observations we will discuss the origin of water emission in high-mass protostellar objects and will use these results to further contrain the origin of high-mass stars and accompanying clusters. This detailed investigation will also serve to discuss the origin of water emission from other Herschel-HIFI observations of (more distant) high-mass protostars.< Réduire