WOW, colliding with another canopy at 300 feet (give or take) will get your heart rate going... and may require a fresh pair of underwear. Luckily there were no entanglements, which could've been fatal at that altitude.
Aside from the generic statement, "stay alert and keep your head on a swivel," there are a few factors that can lead up to an incident like this. We try our best to create proper horizontal and vertical separation between groups when exiting the plane and at break-off, but once we're under canopy there are choices we make that can either increase or reduce the separation we've created for safety during the skydive. If we all try to land in the same spot, or land close to the hangar because we don't want to walk far, or spiral to get down faster, or don't want to get our feet wet in the puddles or pond, then you might find yourself in a situation like this.
Food for thought.