Fukuryu

Only twelve hundred men had been trained when Japan surrendered before the invasion of the Japanese mainland occurred.

They would be weighed down with 9 kg (20 lb) of lead and be sustained by liquid food and an air purification system with two 3.5-liter bottles of oxygen at 150 bar (2,200 psi).

[2] Men were to be armed with a Type 5 attack mine containing 15 kg (33 lb) of explosives, fitted to a 5 m (16 ft) bamboo pole.

[2] Surprise was essential to avoid comparatively simple anti-personnel explosive countermeasures previously used to discourage Italian frogmen in the Mediterranean.

These larger stations would have been manufactured ashore in a variety of shapes to avoid detection, and then sunk at depths of less than fifteen meters.

Only twelve hundred men had been trained when Japan surrendered before the invasion of the Japanese mainland occurred.

American Amphibious Gunboats of World War II: A History of the LCI and LCS(L) Ships in the Pacific.