Regarding the Search and Rescue, and having spent many hours doing Visual Searches for missing ships and the like, it is usual to find pallets and stuff like that on the high seas, things get carried by sea currents, and get scattered all over the ocean. Unusual stuff I have seen in the North Atlantic 100+ miles from the Azores include whole tree logs, containers, plastic crates, plastic boots, ropes, fishing nets (lots and lots), etc, etc
As I was watching the images of a ship in the Search Area yesterday on TV, the Search conditions were not good, quite heavy seas. As a P-3 Pilot said already, most of the times you catch an object by difference of contrast, because you are searching for a white greyish object, in a gray sea with withe/gray foam, under gray skies... You don't "see" it, your eye usually captures the different contrast and you then focus. Also, you get very tired very fast, after scanning for one hour you are mentally fatigued and your efficacy drops, we usually have the crew swap places in the cabin to "change gears".
Also, "good weather" may not be good for SAR, if you have sunlight reflection off the water, it gets difficult to spot objects "down sun", so according to sea state a cloud cover may actually help, although in their case I don't think they'll have a calm sea anytime...