Porpoise sightings could be related to tidal surge

It is unusual for five animals to be in the river...as porpoises tend to be seen alone, and in smaller groups. It isn't possible to say whether the tidal surge is the cause of the porpoises being in the river, but it could well be related, either to the tidal movement, or as a response to the particularly rough seas beforehand. The outer Thames Estuary would have been relatively sheltered from northerly offshore winds. The pod should be able to navigate back to sea, and pass through the Thames Barrier when the tide goes out and the barriers are opened.