In James Lee Burke's The Tin Roof Blowdown, different characters mention an under water glow(ing) in connection with the drowned people near the church where LeBlanc was murdered. It seems to me that there is no answer in the novel as to what these people watched or saw? Is that correct?
It does seem difficult to identify the answer to what causes the luminescent glow, "like fish that could glow in the dark," identified by various characters after LeBlanc is attacked by Melancon on the roof of the flooding church building. Even the protagonist Dave Robindheaux is stumped for an explanation as he asks others what it might be:
"Bertrand Melancon says he saw luminescent bodies under the water in the Lower Nine. You hear of anything like that? ... Melancon said Jude Leblanc caused the bodies to glow."
The main purpose of the "glow" phenomenon is to drive the investigation that Robindheaux conducts and that revolves around LeBlanc's murder.
"[Melancon's] got the Furies after him. He saw of did something out there. Maybe he committed a homocide."
Even though the question of the glowing, fish-like phenomenon seems to be left somewhat of a mystery by Burke, there are two or three reasonable solutions for the puzzle of what the characters saw when they looked into LeBlanc's burial waters--the burial waters of Hurricane Katrina--and saw glowing shapes.
Chemotherapy: It is possible that Burke used the phosphoresent glow to represent LeBlanc's cancerous prostate. Chemotherapy for prostate can increase body-phosphorous levels, causing hyperphosphatemia, one of the causes for which is cell destruction from chemotherapy.
Symbol of Blood Diamonds: The glittering glow might act as a symbol of the blood diamonds that provide one of the problems in Burke's complex plot. Diamonds glow. The waters covering one of Melancon's crimes glows. Blood diamonds are thus symbolically linked to the crimes of Melancon and, simultaneously, to the devastation of Katrina.
Symbol of Toxic Contamination of Post-Katrina Waters: Many toxins were released in the sweep and crush of Hurricane Katrina. The National Academy of Engineering explained "The Aftermath of Katrina":
Adding to the potential sources of toxics and environmental contaminants are metal-contaminated soils typical of old urban areas and construction lumber preserved with creosote, pentachlorophenol, and arsenic. Compounding these concerns is the presence of hazardous chemicals commonly stored in households and the fuel and motor oil in approximately 400,000 flooded automobiles. Uncontrolled biological wastes from both human and animal sources also contributed to the pollutant burden in the city.
Consequently, the glowing, shimmering (like fish) luminescence could easily symbolize the pollution released on New Orleans with the hurricane. An additional layer of symbolism might be the moral and spiritual pollution released New Orleans as a consequence of the devastation of Katrina. Ironically, that pollution might be seen as coming from within, from inhabitants who released themselves to crime and depravity, and from without, from the government that had released neglect and undeclared martial law on New Orleans.