This video from Scotland says about itself:
Very little is known about harbour porpoises during the winter months, as they are difficult to spot in rough seas and poor light of the short winter days. On rare calm days, such as 22 November 2015, they can be seen close to shore, occasionally with calves present (mother and calf swimming close together in this video). If you see harbour porpoises or any other cetaceans please report them to us on our website.
This video was recorded from a sea kayak, drifting past the porpoises with the tide. While they are shy of most boats, if you are patient and respectful you may be lucky enough for them to approach you.
Harbour porpoise beached on Dutch ameland island: here.