David Loewenberg has acquired the moniker “Mr. Cool.”

Beacon: Summer Sunsets & Joie De Vivre

He has acquired the moniker “Mr. Cool.”

But after two decades at the helm of Sag Harbor’s Beacon — the restaurant celebrates its 20th season this year — restaurateur David Loewenberg could more adequately be called “Mr. Smart.” How else could he have turned a trio of restaurants (Beacon, Fresno, and The Bell & Anchor) into a Hamptons juggernaut?

Loewenberg has a storied reputation in the Hamptons. At 28, he opened 95 School Street in Bridgehampton, which has since closed. Later, he went on being a co-partner of Southampton’s Red Bar and Little Red, which his former partner, Kirk Basnight, now owns outright.

A few notes about Loewenberg: He always appears nonplussed, often showing up to service at Beacon in the height of season wearing jeans and Birkenstocks. He may have time to chat — he may not. In the off-season, when Beacon is no longer operational, you’re likely to find him at The Bell & Anchor in Noyac, especially on Sundays, when the restaurant hosts its weekly dollar oyster fest.

Loewenberg’s restaurants feel both upscale and approachable, and that’s why they work. At Beacon, which traditionally opens a few weeks before Memorial Day weekend and stays open through the Columbus Day holiday, there is almost always a line. This owes, in large part, to one of the most coveted dining views in the Hamptons.

A table-wide deck runs along one side of the restaurant, which is also outfitted with panoramic windows. The restaurant hovers over the water and enjoys a perfect sunset every night that the weather cooperates. Arrive before 8 and you’ll almost certainly hear a common refrain: One hour, maybe more.

But you’ll probably wait, and you’ll be glad you did, and not just because of the spectacular show that Mother Nature hosts in front of Beacon diners every single night of the week. You’ll wait — and keep waiting — because Beacon is the kind of restaurant that makes you feel good, that inspires a certain summertime joie de vivre.

The bar is small and sometimes several deep, but you’ll clink glasses with strangers, watch the orange orb sink into the bay, and, eventually, take up residence at your hard-fought table.

Aren’t you glad you stayed?

What makes Loewenberg so compelling and, indeed, so successful? For one, he embraces a local ethos, sourcing seafood and vegetables from East End purveyors when possible.

Since Beacon’s season lasts only a third as long as Bell & Anchor’s and Fresno’s, the restaurant changes its menu with relative frequency, basking in the glory of high season and the bounty it produces. The menu is no-nonsense, the portions generous. The vibe is convivial, revelry without the frills.

Chef Sam McClelland co-owns Beacon and executes its menu, too. This season, he has featured such dishes as local fluke crudo with Mecox asparagus, radishes, lime, and togarashi, and lobster thermidor toast. The restaurant professes a certain Asian influence, incorporating ingredients such as red curry paste, ginger, hoisin, kohlrabi, and soba.

If you’re wondering how a restaurant like Beacon — seasonal, popular, and ever difficult to get into during prime time (they don’t take reservations) — has survived the many vicissitudes of time, the answer is more than just the jaw-dropping view.

The food at Beacon has always been reliably delicious, the prices inoffensive (this is the Hamptons, after all), the hospitality contagious.