  Nonlinear wave focusing originating from the universal modulation instability
(MI) is responsible for the formation of strong wave localizations on the water
surface and in nonlinear wave guides, such as optical Kerr media and plasma.
Such extreme wave dynamics can be described by breather solutions of the
nonlinear Schr\"odinger equation (NLSE) like by way of example the famed
doubly-localized Peregrine breathers (PB), which typify particular cases of MI.
On the other hand, it has been suggested that the MI relevance weakens when the
wave field becomes broadband or directional. Here, we provide experimental
evidence of nonlinear and distinct PB-type focusing in standing water waves
describing the scenario of two counter-propagating wave trains. The collected
collinear wave measurements are in excellent agreement with the hydrodynamic
coupled NLSE (CNLSE) and suggest that MI can undisturbedly prevail during the
interplay of several wave systems and emphasize the potential role of exact
NLSE solutions in extreme wave formation beyond the formal narrowband and
uni-directional limits. Our work may inspire further experimental
investigations in various nonlinear wave guides governed by CNLSE frameworks as
well as theoretical progress to predict strong wave coherence in directional
fields.
