  According to Kelvin, a point pressure source uniformly traveling over the
surface of deep calm water leaves behind universal wake pattern confined within
$39^{\circ}$ sector and consisting of the so-called transverse and diverging
wavefronts. Actual ship wakes differ in their appearance from both each other
and Kelvin's prediction. The difference can be attributed to a deviation from
the point source limit and for given shape of the disturbance quantified by the
Froude number $F$. We show that within linear theory effect of arbitrary
disturbance on the wake pattern can be mimicked by an effective pressure
distribution. Further, resulting wake patterns are qualitatively different
depending on whether water-piercing is present or not ("sharp" vs "smooth"
disturbances). For smooth pressure sources, we generalize Kelvin's stationary
phase argument to encompass finite size effects and classify resulting wake
patterns. Specifically, we show that there exist two characteristic Froude
numbers, $F_{1}$ and $F_{2}>F_{1}$, such as the wake is only present if
$F\gtrsim F_{1}$. For $F_{1}\lesssim F \lesssim F_{2}$, the wake consists of
the transverse wavefronts confined within a sector of an angle that may be
smaller than Kelvin's. An additional $39^{\circ}$ wake made of both the
transverse and diverging wavefronts is found for $F\gtrsim F_{2}$. If the
pressure source has sharp boundary, the wake is always present and features
additional interference effects. Specifically, for a constant pressure line
segment source mimicking slender ship the wake pattern can be understood as due
to two opposing effect wakes resembling (but not identical to) Kelvin's and
originating at segment's ends.
