Meet the newest ocean sensors: elephant seals. These zigzags represent the migration patterns of 11 females between Baja California and the Gulf of Alaska. iPod-size satellite tags glued to their heads recorded the depth, temperature and salinity of the water they swam through and then relayed the data to researchers. The Tagging of Pacific Pelagics initiative, a program of the Census of Marine Life, plans to outfit 23 marine species, including bluefin tuna and white sharks, with 6,000 tags by 2010. One surprising finding so far: A weird warming of California coastal waters in 2005 forced tagged sea lions to venture offshore up to 300 miles in search of food.