It seems that there are many more seals in the Thames than we thought! A study, found here, by the people at London Zoo has been mapping seal locations in the Thames Estuary.
This is a GIS (Geographical Information Systems) map, click on it to go directly to the main website. Pictograms are used to locate seals, either dead or alive, you can then click on the individual seal to find out more information about the sighting and the seals. There are also links to the way in which the data has been collected.
There is nothing new about combining data sets to present on maps, however the interactive nature makes the depth of information much more accessible. In addition data on seal sightings can be communicated by members of the public via twitter which allows large amounts of data to be collected a little cost.