Some drops don't splash

The work reported in this paper shows that when a drop of water enters a pool of water two different phenomena may be observed depending upon the diameter and velocity of the entering drop. In one case the drop causes a splash and in the other case the drop coalesces with the pool without a splash and as the drop penetrates the surface it forms a vortex ring. The occurrence of the existence of the two phenomena has been characterized by a combination of the Froude number and the Reynolds number.