This frame grab from video tweeted by Elon Musk shows a “tiny kid-sized submarine” being tested in a pool at Palisades Charter High School, Sunday, July 8, 2018, in Pacific Palisades, Calif. Musk’s Space X rocket company tested the submarine that could potentially help rescue the remaining children and their coach trapped in a flooded cave in Thailand. (Courtesy of Elon Musk via AP)

Super entrepreneur Elon Musk has built a small submarine to save the boys that are trapped for more than two weeks in a flooded cave in northern Thailand. But it is unlikely to be used.

Elon Musk sends the mini-submarine to Thailand for safety, although it is unlikely to be used, Ars Technica report.

The boys have been trapped with their trainer in the cave in northern Thailand for several days. Five boys have been rescued by divers and the rest of them hopes to be rescued in the same way within the next few days.

But Elon Musk has been working on alternative rescue methods. Musk took to social media to demonstrate its child-sized u-boat, built using the liquid oxygen tank used on the Falcon rocket.

The vehicle’s diameter is 31 centimeters. “Sufficiently easy to be carried by two divers, small enough to get through small passages and extremely robust”, he tweeted.

Elon Musk ordered engineers on Space X this weekend to start building the vehicle so it would be completed within a day or two. But when the u-boat had finally finished, the Thai rescue operation had already started.

Musk decided to move along anyway, “even though it might not become useful here, maybe it will be in future situations”. On Sunday he posted pictures on the u-boat, as well as movies when tested in a pool. It reached Thailand on yesterday, Monday.

In the twitter flow, Elon Musk receives a lot of praise for his initiative, but he is also accused of exploiting the boys’ situation for publicity.

Another method of saving the boys is tested locally at the cave. The Independent report about an inflatable nylon tunnel that can be collapsed and dragged into the cave system and then blown up with a big fan in the cave. Now it is tested to see if it is durable enough to handle the edgy edges of the cave.

Thai authorities say a former Navy SEAL working to rescue the boys and their soccer coach trapped in a cave died from lack of oxygen.

Update: All boys evacuated from the cave.