The other day we had a very typical mother calf pair sighting. Mama and baby were swimming right next to each other for several minutes at a time, then diving down together where they remained underwater for another several minutes, coming up for air again nearby. It took a few surface series before we realized that the mom had a rope wrapped around her tail and was trailing a buoy. This could have a big impact on her ability to dive, and to properly care for her calf.
Entanglement in fishing lines, nets, and other debris floating freely in the ocean is a real
problem for whales and other marine species. Recently a dead humpback whale calf was spotted floating in the Gulf of Panama, with a net entangled around its tail stock.
Read more about marine debris here:
http://marinedebris.noaa.gov/marinedebris101/mdinfo.html