Emergency warning for boats after dead whale is spotted floating in the Thames A dead whale has been spotted floating in the Thames Estuary, prompting Coastguard officials to issue a navigation warning to vessels in the area. The mammal, believed to be a humpback, was found by a passing tugboat off the Isle of Sheppey in Kent at 7.30am this morning. Humpback whales have a wide-ranging habitat, but they near to the coastline, feeding on krill, plankton and small fish. They can grow to up 19m in length and weigh 40 tons. Officials from the Port of Sheerness are now trying to recover the whale before a post-mortem examination. A Thames Coastguard spokesman said: "It's running with the tide so it will go out eastwards if it is not lassoed. The Port of Sheerness, whose jurisdiction it falls under, are looking to recover it and bring it ashore. It looks likely that it will be post-mortemed to find out why it died. We have issued a local navigation warning. Obviously for larger vessels, the whale isn't going to present too much of a problem. In 2006, a stranded northern bottlenose whale delighted crowds after making its way up the Thames to central London. But tragedy struck when the 19ft creature died from dehydration, muscle damage and failing kidneys after being unable to feed for three days.