I fear the Harkles will be both hurt and disappointed by your failing to recollect the charming tale that Hazza shares with us in Spare.
After an evening spent with the King telling them stories of selkies (shape-shifters who appear as seals or beautiful women), the Harkles walked romantically on the beach the next day. Hazza tried singing to the seals in the hope that he could summon the selkies, but they blanked him. However, when his beloved burst into song, the seals appeared in abundance. The simple Prince took this as firm evidence that his beloved was truly magical. There is no mention of what she sang, but there is some speculation that it was 'Money (That’s what I want)' - the Lene Lovich version.
The happy couple returned to the castle where they encountered a grumpy chef who told them it was irresponsible to lure the seals close to the shore as they would be killed by orcas. That is to say killer whales, not Oprah Winfrey.
Fortunately, the chef did not dampen the ardour of the love-struck Prince.
However, this is the North Sea we are talking about and it is still true to say that vampires cannot cross running water.
The King had shared stories of sirens disguised as seals with the Sussexes the night before the encounter during a holiday in Scotland
www.telegraph.co.uk