Creatures of the Ledge
The course of your diving, you may have peered into ledge structures, and noticed that many have similar mini-ecosystems operating within them.

When we drift dive in Palm Beach county, a great deal of it involves allowing the current to carry us along over the inshore facing edge of the many miles of north-south trending reef body. This inshore edge where the reef crown comes to an abrupt end, is cliff-like in most places, and frequently the face is pitted and hollowed out, with huge ledges and major undercuts forming everything from crevices to cavern like homes.
As we glide along, frequently we will come to a section which is begging to be explored up close. Even a smaller crevice can have some fascinating life inside it.
The larger undercuts are homes to schooling fish, but frequently with uninvited guests which are happiest when dinner doesn't notice them in time.
Lobster are typical creatures of the ledge and crevice system here. They hang out by day in tiny undercuts and fissures with deep escape routes and just enough room for the lobster to pass through (not enough for its larger predators).
Related to the lobster, but with an entirely different behavior and lifestyle are the shrimp. They will hang around the larger ledges and undercuts where larger fish tend to rest from the current. The shrimp advertise their presence, and fish will swim up and allow the shrimp to "clean them" (i.e., consume the para sites they can remove from the fish) like this moray eel at a cleaning station, pictured below.
A healthy reef system has lots of these little cleaner stations. To find the shrimp, look for ledges on the lee side of the current, and for large fish hanging motionless right by the ledge. If you approach slowly without scaring the fish (try appearing disinterested to them- -fish frequently know when they ar e being looked at), you may get close enough to see the small cleaner shrimp at their station.
Once you have found them, you realize these tiny creatures are really quite fearless. .
The shrimp will walk right up on your hand....
...Or into the mouth of a huge fish hundreds of times its own size.
While we find many large fish in this part of the reef, we also find many tropical sized fish, who inhabit these areas full time, and who will defend their territory as fiercely as a Century Villager will defend their parking space (sorry, only Florida residents are likely to get this analogy).
This Blue Hamlet is one of the more timid inhabitants.
This Blenny is another one of the more cautious personality types we find hanging out in the protection of the ledge.
The Spotted Drum is a much more approachable ledge inhabitant. If you swim in slowly, they will usually just watch you, and sometimes even come closer to investigate you.
Copper Sweepers are very easy to find under the dark undersides of the ledge overhangs, and you will find them quite oblivious to your approach.
Turtles are often found sleeping in ledge overhangs, which makes them extremely easy to get close to.
Another inhabitant you'll have no problem getting too close to is the Sea Urchin---divers with poor bouyancy skills can easily get too close for comfort!.
As you focus down and begin to look for the smaller life forms, some of them appear to be very complex, and "other worldly" looking.
A whole new ecosystem begins to unfold within this ledge structure.
From the world of a Squat Anemone Shrimp...
...To the camoulflaged existance of the Frogfish...
...And the shy but highly predatory life of the Octopus...
...The creatures we find in the ledge systems of South Florida are worth slowing down to take a close look at....
A whole new ecosystem begins to unfold within this ledge structure.