I am a part time employee of BainBridge Sportsman Club, I speak on my knowledge of talking to the owner regarding the sign to clear up rumors before they start. The rest of the information in this post does not reflect anything that BSC may or may not believe. The rest is my own rambling.
The signs state the following: Reels are not allowed on the platforms or in student areas. The signs came about as part of the incident that happen
The reason for this is the chance of entanglement is very great in those areas due to cables, ow students, trees, attractions, attraction lines and so on. The lake is over 27 acres and only two areas really fall into this classification. The first area is the lagoon. The lagoon is a semi isolated section that reaches a max depth when the water table is high of 20 feet. Vis in there drops fast when students are present and this could cause issues with running a line in that section. The next section is what is refereed to the bowl. you reach this section by either swimming through the lagoon, going up and over the under water road (depending on water table) and following the quarry wall to the right. The other way to this area is to walk down the path and enter from the tip. In this section there are several platforms at various depth. The deepest it reaches here is around 45 feet (once again depending on water table). This section is littered with attractions from when the quarry was a quarry as well as items put in for divers. There is also lines running from platforms and attractions. This area could easily cause a experience reel user to become entangled, or cause a student to think your line is a attraction line and become lost or entangled as well.
The remaining part of the lake is open for the use of reels. Side note when running a reel make sure to tie it off every few feet to avoid free floating line and to help not loose your full path back if one section breaks. If you are using the reel to deploy bags make sure you are in a section where there are no over head entanglements or students.
For those that ask about the divers certification levels, it really does not matter. Each diver is made to produce a cert card that has a photo on it. If they are new to the lake and ask they are given a a quick run down on depths and attractions base on their skill level. Their are signs around the property that warn of diving with in your limits and not to exceed certain depths, with a restriction that no dive should be below 90' feet (lake reaches 130 feet, most deep attractions are no deeper then 100 feet). Even with all these precautions there are no such things as scuba police. Once a diver gets down to the lake the dive they plan and execute / try to execute is their responsibility.
Unfortunately as in this case errors happen that cause injury and or death. The error chain in recreational diving is a bit longer then in deep or technical diving. Those that are in shallower depths have more time and a clearer head to try to work out a issue then those that are down deep and run into problems.
My prays go out to the divers family , friends and dive buddy.
Remember a good diver is always learning and aware of their surroundings.