Well, first of all, it is necessary to clarify that there are no square bricks, therefore it is not possible to throw this object of the specified shape into the water. Brick, as a rule, has the shape of a parallelepiped. It can fall into the water at different angles, plunging in different ways and, thus, being projected onto the surface of the water in the form of various geometric shapes. But is it so important whether a circle, a square, a triangle or a trapezoid falls on the surface of the water? Most often not.
The fact is that in the first moments of a brick falling into the water, the waves repeat the shape of the geometric figure with which the brick was projected onto the surface of the water. However, as a result of the action of water tension forces and due to the adhesion of water molecules, the waves, propagating and overlapping each other, will take on a spherical shape. Of course, this can only be observed when shooting with a camera and then slow-motion viewing the footage. In addition, as a rule, the dimensions of a brick are negligible compared to the dimensions of the surface of the water, so a brick can be taken as a point, and its shape in this case practically does not play any role.
For those who are thirsty for a more scientific explanation of this phenomenon, I recommend that you familiarize yourself with the Hugens-Fresnel principle, which is the main postulate of wave theory, which describes and explains the mechanism of wave propagation and not only on water.
In general, it should be said that the spherical shape is the most optimal in nature. Note that hanging drops are also not square or triangular …