Later, during a brief news conference, he repeated the assertion.

“Frankly, we’re doing — and it’s the most difficult job because it’s on the island — it’s on an island in the middle of the ocean,” he said. “It’s out in the ocean. You can’t just drive your trucks there from other states.”

That’s true. Instead, supplies must be transported by airplane or ship instead of by truck. But that’s still not a great excuse for why the island is awaiting supplies.

FEMA is coordinating airlifts from U.S. Air Force C-17 cargo planes into Puerto Rico, bringing food and water. An update from the agency on Monday indicated that eight aircraft were delivering relief supplies and cargo to both that island and the Virgin Islands. Each aircraft can hold some 100,000 pounds of cargo.

That’s important. But there’s a way to scale that up. In January, a cargo ship operated by the U.S. Navy delivered supplies to researchers in Antarctica totaling nearly 7 million pounds of supplies.

So couldn’t the government have either sent supplies in advance (as it did for Texas and Florida by truck) or sent cargo after the fact that could have gotten to Puerto Rico by now?

The answer is yes and yes.

To the second question first. The ship-tracking site MarineTraffic.com provided The Washington Post with data on two ships that left the continental United States after Maria made landfall in Puerto Rico and which either have arrived or will soon arrive there. The first is a cargo ship — the truck of the sea, if you will — named Perla Del Caribe. It left Jacksonville on Sept. 22 — two days after Maria landed — and arrived in San Juan on Tuesday afternoon.

The second is a tanker, the Overseas Long Beach, which left Houston late on Sept. 21 and was to arrive late Tuesday night.

In other words, ships loaded with supplies could have been in Puerto Rico by now even if they hadn’t departed the mainland before the storm struck the island. The trucks, if you will, could have driven there by now.

But the government could also have stationed ships closer to Puerto Rico in expectation of needing to offer aid. By Sept. 16, the National Hurricane Center was already expecting Maria to hit Puerto Rico “as a dangerous major hurricane” — only a week after Hurricane Irma brushed past the island, killing three. Ships with supplies could have been stationed nearby.

Isn’t that dangerous? Ships avoid being in the direct path of a major hurricane for obvious reasons, including that a ship called the El Faro sank during Hurricane Joaquin in 2015. But as Popular Mechanics explained in 2014, mariners are prepared to seek out safe ports as needed or to move out of the storm’s most dangerous path.

“If a ship is in the ocean, you’re going to have heavy weather,” chief meteorologist at Ocean Weather Services Fred Pickhardt told the magazine — noting that ships often operate on tight schedules that make days without progress an economic challenge. (Even the company that owned the El Faro told CNN last year that it wouldn’t demand that its replacement vessel necessarily avoid a hurricane that was approaching but that it had “great confidence” in its captain.) Our government supply ships, of course, would not feel the pinch of needing to stick to a schedule and could presumably wait out the storm in a safe location nearby.

Many ships did just that as Maria approached.

In fact, our Dan Lamothe notes, this is precisely what two U.S. Navy vessels already in the area did. The USS Kearsarge and the USS Oak Hill, nearby to assist with relief from Irma, moved south to avoid the direct path of Maria and then returned to provide assistance to Puerto Rico.

Having supply vessels on the ready would have required preparation on the part of the government, as well as foresight as to how much damage Puerto Rico might incur. But, again, that’s what Trump’s administration did with its trucks, as he noted on Twitter before Hurricane Harvey hit Texas.

These are complicated calculations that appear much easier in hindsight. It is not the case, though, that there was no other option for Puerto Rico than what it is experiencing right now, no matter what the president might argue.

Update: Late on Tuesday, Lamothe reported that the Comfort would soon depart for Puerto Rico.