• Ukraine unveiled a new model of its Sea Baby drone.

• It is more maneuverable than the original and can carry 2,200 pounds of explosives up to 621 miles.

• Sea Baby drones have inflicted a series of humiliating defeats on Russia's Black Sea fleet.

Ukraine has upgraded its Sea Baby drone after it inflicted a series of humiliating defeats on Russia's Black Sea fleet.

"The Sea Baby 2024 is a new-generation drone that is enhanced and even more lethal for the enemy," said Ukraine's SBU military intelligence agency in a statement, according to a translation by Ukraine's Defense Express.

According to the SBU, the Sea Baby 2024 is more maneuverable, can be fitted with weapons, and is able to carry around 2,200 pounds of explosives up to 621 miles.

The SBU said 25 of the new drones had been built and are being tested with the help of $7 million in crowdfunded donations.

It also released a video showing the vessel changing direction at high speed in the water.

The original model appears to have had a similar range and payload, though not the maneuverability or weapons capabilities of the new model.

Ukraine's sea drones have been central to its success against the Russian navy in the Black Sea.

The vessels are remotely piloted using GPS and cameras, fitted with explosives, and driven into ships. They are relatively cheap and around $200,000. Other weapons used to target warships, such as missiles, can cost millions of dollars.

They can also be adapted and upgraded, experts told Business Insider in January.

Ukraine claims to have sunk or disabled around a third of Russia's fleet, or 27 vessels, despite having virtually no navy of its own.

The SBU said in its statement Wednesday that sea drones had been responsible for sinking 11 Russian ships, as well as blowing up the Kerch Strait bridge in an audacious attack last July.

The successes have helped Ukraine open up a corridor for vital grain exports.

The latest success came on Tuesday, when a Ukrainian sea drone sank the Sergey Kotov, a Russian patrol ship, off the coast of Crimea.

On the ground, however, Ukraine is struggling against Russia. Its forces are facing ammunition shortages as Republicans in Congress block $60 billion in aid. Russia is seeking to take advantage of the situation by intensifying its attacks.