Given the lack of (life sustaining/growth promoting) sunlight in the depths where the Electra wreckage is presumed to lie, I would expect the affect is negligible.
I guess that depends upon what depth the Electra wreckage is presumed to lie and whether whatever is left includes aluminum. We have a number of possible pieces of debris at a fairly broad range of depths:
• The Cook Object at about 18 meters (60 feet). Lots of light and marine growth
• Glickman's landing gear debris field at about 61 meters (200 feet). Still plenty of ambient light and marine growth at that depth.
• Richie's anomaly at about 187 meters (613 feet). Very little sunlight penetrates to that depth and new coral growth is minimal. If the anomaly is aluminum aircraft wreckage I would expect it to be largely free of coral or plant growth.
At 250 meters (820 feet) and below, it's a cold, dead, dark world with a constant light "snowfall" of talus from above that covers some, but by no means all surfaces, with a light dusting. If pieces of aircraft wreckage ended up that deep I would expect them to look much like the Norwich City wreckage that is at a similar depth, easily recognizable against the natural background except I would expect the aluminum to be largely free of growth. The idea that pieces of aircraft wreckage would be so encrusted and coated as to only hint at the shape of the underlying object is, as far as I know, contrary to anything we see in the Norwich City debris field.
It is also possible, and there is some reason to believe, that the aircraft broke up in relatively shallow water and most, if not all, of the sheet aluminum was carried away to be later washed up, salvaged, and used up by the locals, or widely scattered southward "downstream" by natural forces. That's what TIGHAR member Howard Alldred theorized. Howard was a geological engineer from New Zealand with extensive knowledge of coral atolls. He was an EPAC member and was on the 2003 Niku VP expedition. Tragically, Howard later died of a brain tumor. It was Howard's scenario that prompted TIGHAR's own senior archaeologist to argue strongly against us even trying to find the plane.
If Howard's scenario was correct, the surviving wreckage may be analogous to what we saw in Idaho last summer during the
Field School. In that case a Lockheed Electra was forcibly disassembled (by colliding with a mountain) and the aluminum structure subsequently removed (by fire and human salvagers), leaving behind only the heavy steel components - landing gear pieces and engine parts. If that's all that is still there we have our work cut out for us but, even so, I think the subs can do the job.