This video from the Netherlands says about itself:
29 July 2016
This afternoon, SOS Dolfijn received a report about a swimming harbour porpoise in the canals of Den Helder in the northwestern part of Holland. Our team is on location to observe and assess the situation. We are ready to offer help if necessary. The animal is behind the sluice-gates and might possibly find its way back to sea. Also it could be an animal in need and distress. An update will follow.