The rock rises out of the water about a kilometre from Tel Aviv beach. It is sharp and serrated, and only desperate hands – the hands of a drowning man – would dare to grasp it. From an outsider’s perspective, my perspective, the perspective of a woman standing on dry land, what happened on this rock is simply impossible. How on earth could it have supported not one but two men, for long, endless minutes, in a life or death battle?

The year is 1939. The Mediterranean is deep and blue. Tel Aviv’s shores are under the control of the British mandate and British law has forbidden Jews from entering the country. Those who manage to escape Europe find Palestine’s borders closed to them. Ships are sent back to the continent – only for some of their passengers to find themselves in the Nazi death camps.

Peter Kosminsky: Britain's humiliation in Palestine Read more

The only hope, then, is illegal migration. At night, the refugees arrive some way off the coast. Hidden by the darkness, they slip out of the boats and attempt to reach the shore. The fear of being caught by British officers is secondary. For the refugees there is a bigger problem – few of them know how to swim.

The Jews of Tel Aviv are keen to help their European brothers. In the middle of the night they sneak into the water. They are strong, they know the sea. They carry the newcomers on their backs. My grandfather was one of those good swimmers. He was an athletic high-school student, who found that he generally preferred smuggling refugees to studying for his final exams. But on one of these nights, he almost drowned.

Reaching a boat, he loaded one of the men on to his back. The guy was around his age, he told me, thinner than a starved goat. Carrying him wasn’t supposed to be a problem. But as he started to swim, my grandfather realised he was sinking. The man on his back was skin and bone, but he dragged him down as if he was made of lead. “Are you carrying anything?” my grandfather cried. The guy nodded. “You were told to leave all luggage on the boat – do you want both of us to drown?”

The refugee didn’t want them to drown, but at the same time he refused to let go of his bundle. That was when my grandfather, utterly exhausted, reached the sharp rock. “Look, you idiot, I’m not going to die for your family treasure. Throw the bloody thing into the water, and let’s get to land before the Brits catch us.”

It was then that the refugee told him about the statue. He was an art student back in Europe. Before being separated from his family, he’d made a bust of his mother’s head. He couldn’t let it be lost in the waves, he said to my grandfather; he’d rather drown.

My grandfather wasn’t a big fan of figurative sculpture. He knew they had to get to the beach before sunrise, or they’d find themselves at the mercy of the border police. He decided the only option was to stun his charge with a punch, and then swim with him to land. But the man saw it coming. They started struggling. It turned out that the starved goat was much more powerful then he seemed. For a moment, my grandfather thought that the jagged rock would be the last thing he saw.

“Stop it, you’ll get us both killed! All right,” he relented, “we’ll carry the damn thing with us!”

I have no idea how they did it, but when the sun came up that morning, they were already on land, blending into the crowd to fool the British who would have had trouble telling the locals from migrants.

Barbados didn’t feel like black man country – till I saw boys walking freely | Chibundu Onuzo Read more

I visited that beach with my grandfather more times than I can remember. And long after his death, I keep going back. For years I thought that my grandfather was the hero of this story. I was so proud of his extraordinary swimming skills, especially as I have the swimming abilities of a Persian house cat. It was only years later I understood that the real hero was the man he carried. The statue that my grandfather wanted him to abandon gave his journey meaning. As long as he kept the statue, it kept him from being reduced to “a refugee” – it reminded him of who he was.

The Mediterranean was a graveyard for hundreds of Jewish people who tried to flee the second world war. Today, the water is the grave for others seeking refuge. And the people on the land still don’t want the people from the water to come in. As I look at this place – the beach, the water, the rock – I ask myself what’s worth drowning for, and what’s worth living for.

• Ayelet Gundar-Goshen is an Israeli novelist. Her latest novel is Liar