reptile name

Question
I live in south Florida and have several reptiles by my home. I can't identify one. They are between 4" to 8" long not including the tail which is about 1 and 1/2 the length of the body and is very thin. It has a crest on it's head and seen to like tall grass or resting in the sun on the palm trees. Now the wierd part, it runs upright on rather large [for it's size] rear legs. The color varys between bright green to motled brown. There are a lot of reptiles here but this is the only one that I can't identify.
Thanks for your help,
Marty

Answer
Martin, what you are seeing are called Basilisks.  There are both green and brown varieties.  They are also called "Jesus lizards" because they run so fast on those back legs that they "walk on water."  I live in central FL and have actually seen one in the wild up here as well.