  In the limit of small values of the aspect ratio parameter (or wave
steepness) which measures the amplitude of a surface wave in units of its
wave-length, a model equation is derived from the Euler system in infinite
depth (deep water) without potential flow assumption. The resulting equation is
shown to sustain periodic waves which on the one side tend to the proper linear
limit at small amplitudes, on the other side possess a threshold amplitude
where wave crest peaking is achieved. An explicit expression of the crest angle
at wave breaking is found in terms of the wave velocity. By numerical
simulations, stable soliton-like solutions (experiencing elastic interactions)
propagate in a given velocities range on the edge of which they tend to the
peakon solution.
