Elon Musk's Space X rocket company has dispatched a "kid-sized submarine" that could help boys trapped in a flooded Thailand cave.

Musk posted of the aluminum sub being tested at a swimming pool Sunday midafternoon California time. Following the tests, that the sub was placed on a 17-hour flight to Thailand.

Four of the boys were rescued on Sunday. Four ambulances left the area of the flooded cave on Monday, suggesting that a total of eight of the 13 trapped people have now been extracted.

A spokesman for Musk's Boring Co. tunneling unit, which has four engineers at the cave, has said Thai officials requested the device, which could potentially help the children through narrow, flooded cave passageways.