Dive
A dive is a move that can be performed in midair to cause Mario to lunge forward. It can be initiated by pressing X or Y while Mario is in the ground pound animation in midair. Most often, dives are performed by pressing X or Y immediately after pressing ZL or ZR to ground pound.
Properties
Performing a dive causes Mario's height to increase by 182 units[1], which makes them useful for diving up onto a ledge at the end of a vertical trickjump. Dives also propel Mario forward a fair amount, and this happens to be the perfect distance to hit Cappy after throwing him to perform a cap bounce.
After diving, there is no way to cancel the dive animation until Mario touches the ground.