A Philly artist created a giant sculpture of his father’s head that disappears with the tides. Imagine his father’s surprise.

The other night by the Delaware River, the giant translucent sculpture of Ardmore jeweler Alexander Horn’s head seemed nearly about to drown, the tide having risen up over his chin, soaking his trimmed beard and lips and covering his elegant nose.

His eyes were still above water, as if paying attention, maybe a bit relieved, as high tide was once again receding inside the rainy boat basin, where a spellbinding art installation has replaced the beer-and-hammock masses of Spruce Street Harbor Park.

Horn, a 68-year-old fixer of clocks, is also paying attention in real life. Wouldn’t you, if your artist son, Miguel Horn, 36, had sculpted a giant, hollow likeness of your head, bald spot and all, and placed it in the Delaware River, set down in the wild of the tides, where the murky water now has you and he debating the depths of your relationship?

Imagine your surprise, if you had not even known that this giant acrylic sculpture your son had been working on all these months inside his Parkside workshop — making up excuses for why you couldn’t just drop in as usual — was, well, of you?

“At the beginning, I could only see half the face,” Alexander Horn was saying. “It was emotional. It was my head, you know.”

The other morning, Horn, in a fedora and stylish wool suit, and his son parked their cars a block away from the water and walked down together to the river. The piece, called Abu, is one of 10 floating sculptural installations outside the Independence Seaport Museum collectively called Flow.

“You want to react with it," Alexander said. "It’s like almost alive, but you’re here. And it’s there.”

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Father and son have come out on the dock on a recent morning to contemplate Miguel’s piece, set to be on display through Dec. 7. It is around low tide, so the entire head is above water, which is good for viewing, but the daily tidal movement has been slowly rotating the entire head clockwise.

They were there only a few days before a freak post-Halloween squall would literally rip the acrylic head from its base, and leave Alexander’s head severed at the chin, stuck in the mud.

But for now, it is the position of the head that is bothering Alexander. From the walkway, where most people will see the piece, the view is of the back of his head.

“Why don’t you fix it?" Alexander says. "For people to see. They walk by, they only see the back. Don’t you want it facing more?”

Miguel agrees only in theory. “I’m not controlling it,” he reminds his dad. “I’d have to come back every single day and push it. And come in at high tide.”

“Maybe you can turn it and swim in there, tie it to the post,” Alexander persists. It seems a bit inhospitable to have his likeness turned the other way to visitors.

But that loss of control is also the point of the work, Miguel points out.

“In this situation, it’s kind of like giving it up to this water, this moving body of water. There are so many things that were totally out of my control.”

When Miguel Horn decided to turn the piece, commissioned as part of a collaboration between Philadelphia Sculptors and the Independence Seaport Museum, into his father, he knew certain forces would be out of his control.

Not just the tides that would gradually turn the head clockwise, and twice daily swallow it, or the silt on the bottom of the harbor that would discolor the acrylic and unexpectedly highlight his father’s features by reflecting the light in a different way.

He was not quite prepared for the hazards of installing the piece, watching as assistants Phil Poles and Quinn Moon lay in rowboats tied to the docks, an October nor’easter lashing at them as they worked to anchor the platform upon which Abu sits, a center pin with a not-quite-tightened bolt allowing it to rotate with the tides but not float away.

And he was most definitely not prepared to be summoned to the site the day after Halloween, to find a freak storm had ripped his father’s acrylic head from the base, leaving it decapitated at the chin, lying on its ear, stuck in the low tide’s muck. “Pretty gruesome,” he said. He called a crane operator who, he said, would hopefully be out in a few days to lift the head so Horn could repair it on site and set it back in the basin.

Horn knew the full experience of his work, at least for him as an artist, would only come when his father saw that the work was of him.

And so he didn’t tell him.

During the month when Miguel was creating the work — a complex process involving computer modeling, 3D scans, algorithms, “a thousand small little acrylic pieces," and “crazy computerized geometrics of bolts” and a team to build it — he and his father were not even getting along, both remember.

When he brought his father to the Oct. 12 opening, Alexander thought the bust was to be of another person. But, even with the work partially obscured, something seemed familiar.

“I said, ‘Wait a second, that’s my little bald spot,’ ” Alexander recalled with a laugh. “I said, ‘That looks like me.’ They all started laughing. I loved it, but the emotions are difficult to express. It was, ‘Is this me?’"

Miguel says his father said, “Why are you sinking me in the water?”

His father later trimmed his beard, more closely cropped his hair, wore his hat to obscure the bald spot.

Miguel was hoping the piece would lead himself and his father into deeper conversation. Like his art, that’s a slow reveal. Feelings open, only to get covered up again.

Miguel looks at his piece and goes deep, thinking about the changing nature of memory, loss, and mortality, and about time, made more pronounced, as with the silt, after his father’s recent health scare.

Alexander takes in this monumental work his son has created and thinks about their relationship.

He likes the way Miguel wrote about the waters appearing clear at times and murky at others. “There’s always hard times and good times. And frictions. We all go through that.” He likes that his son was thinking of him all this time.

Miguel has thought a lot about his father becoming a grandfather to his own son, nearly 2, how he had in the process more fully become the patriarch.

Alexander thought about his own father, an artist himself, a tyrannical sort born in Budapest, who he’s pretty sure would not have liked it if he had done the same as Miguel.

He is, he says, a different father than his own. And Miguel is creating his own map of how to be a father.

Miguel, looking at the severed head after the storm damage, likened it to “a toppled dictator.”

Family friends have started paying attention to Miguel’s art in a way they hadn’t quite before. Alexander booked a table at the restaurant that has a view of his floating head.

The Ardmore Business Association liked it so much they tweeted about it. “It’s not every day you get to see one of our shop owners floating in the Delaware river!” they tweeted about the owner of Alexander Horn & Co., whose shop is on Cricket Avenue.

Alexander says he doesn’t worry too much about the deeper meaning of the daily tides that cover his face, then reveal it, acrylic strip by acrylic strip.

As the low tide rose to his lips the other morning he joked, “Maybe I should stop talking.”

Father and son recalled how Miguel had invited his father to play chess at his studio, a way of sitting while he sculpted a clay bust of him, and it had taken so long, months of chess, because Alexander talked so much, Miguel couldn’t get the lips just right.

As they left in a drizzle, having begun to mine at least a semi-low-tide level of their relationship, Miguel suggested the two go for a coffee and talk some more. “No, Miguel, I’ve got to go ... your mother is waiting for me at the shop,” he said his father told him.

But a bit later, his father had called back. Of course. Because wasn’t that the point of Abu, of placing a giant translucent bust of his father’s head in water that will cover it twice a day — that relationships, memory, feelings, family bonds are revealed and felt differently every hour of the day?

His father had given it some more thought. “He called me and said, ‘We should have gone to get that coffee,’ ” Miguel said.