If it's a mechanical wave, then its speed depends on the physical characteristics of the medium.
If it's an electromagnetic wave, then its speed depends on the
electrical characteristics of the medium.
Either way, the properties of the medium determine the wave speed.
You want to change the speed ? You have to change the properties
of the medium.
The people of Florida are closest to the equator and also near 2 different bodies of water and have rivers running thru them as well salt water and fresh water. they need alot of freshwater due to monsoon seasons, hurricanes etc, its humid and hot there so naturally you need to water more often and frequently.