Talk about adding in-salt to injury.

A Hamptons real estate developer allegedly left pals with horrific injuries after drunkenly crashing his yacht with them inside it — and now he’s suing them, too, claiming the smash was their fault, legal documents show. 

Back in July, Page Six reported that luxury homes mogul Peter Mangiameli allegedly drove his yacht into a Sag Harbor jetty, leaving his passengers unconscious and with broken bones, before disappearing from the scene before cops arrived.

Michail, Dokianos, 51, Elena Dokianos, 51, and Sofia Dokianos, 22, sued him for $6 million over the July 5 crash, claiming in their legal complaint that Mangiameli, 57, was drunk at the helm of his 2024 Cruisers Yachts vessel, “the Déjà Vu,” when he slammed into the stone breakwater around 10 p.m.

Now the Southampton property bigwig — who bills himself as a visionary builder of estates for A-list celebrities, socialites and financiers, with pads fetching up to $22.5 million — is fighting back.

In a counterclaim, he alleges Michail had agreed to serve as first mate and dedicated lookout during the return voyage, including shining a spotlight from the bow to watch for obstructions. Instead, Mangiameli claims in his filing, his passenger appeared “significantly impaired,” dropped the spotlight and failed to retrieve it.

The developer also accuses the father of botching his duties when untying and stowing the boat’s mooring lines. The alleged lapses, Mangiameli claims, contributed to the collision, the vessel’s severe damage and salvage expenses, legal documents show. 

According to the lawsuit, he wants Dokianos to pay up for the boat damage and salvage bill — and reimburse him for damages, legal fees and costs if he loses the family’s suit.

Mangiameli denies the allegations of intoxication, gross negligence and fleeing the scene.

Page Six has reached out to Mangiameli and the Bokianos and counsel for both parties.