The Israeli navy is a bit of an odd duck. It's designed largely for coastal and eastern Mediterranean warfare. But among all of Israel's small corvettes and missile boats are some some seriously mighty submarines.

Israel is also investing heavily in growing its submarine fleet. It's a reflection of Tel Aviv's increasing reliance on the underwater boats for a range of operations — including nuclear deterrence.

Right now, three Dolphin II-class submarines are under construction at Germany's ThyssenKrupp Marine Systems shipyards in Kiel. Once the submarines complete their trials and head towards the Mediterranean, they will become the most powerful Israeli submarines ever.

More than 225 feet long, the diesel-electric Dolphin II class is part attack submarine, part nuclear strike ship and part commando taxi.

They're also painted in an unusual combination of black, blue, and green colors. That's "meant to make the ship less visible, and thought to be especially effective in Mediterranean waters," Defense News noted after recently publishing photographs of the fat, oddly-shaped boats in dry dock and on sea trials.

In terms of weapons, the three boats of the Dolphin II class — the Tannin, Rahav, and a third unnamed submarine — contain 10 torpedo tubes capable of launching fiber optic cable-guided DM-2A4 torpedoes. Germany has already handed over the Tannin.

Four of these tubes are larger 26-inch tubes — the size is rare for a Western-built submarine — capable of launching small commando teams or firing larger cruise missiles. The remaining six tubes measure at 21 inches.

Although not admitted by the Israeli government, the Dolphin II is widely believed to soon possess nuclear-tipped Popeye Turbo cruise missiles. The submarine's armament includes non-nuclear anti-ship Harpoon and anti-helicopter Triton missiles.

In 2012, German news magazine Der Spiegel interviewed several German defense ministry officials, all of whom were under the assumption that Israel intends for these submarines to carry nuclear weapons. The missiles can also be launched "using a previously secret hydraulic ejection system," the magazine reported.

The photographs at Defense News also reveal horizontal planes for trailing communications gear and sonar buoys. But the classified propeller is covered by a tarp to keep out prying eyes.

For sensors, the Dolphin II comes with the German-made CSU-90 active radar, a PRS-3 passive ranging sonar, and a FAS-3 flank sonar. These sensors are in addition to an Israeli-made surface search radar.

Of course, submarines need to be stealthy — and the Dolphin II is indeed quiet. The trick is in the submarine's air-independent propulsion fuel cells, which provide power under the surface as the diesel engines — used for running on the surface — rest and recharge.

This system is quieter than the nuclear-powered engines on American and Russian submarines, which must constantly circulate engine coolant. Nuclear submarines are virtually unlimited in terms of range, and are better used for deep-water operations. But Israel has no need for nuclear-powered subs when quiet diesel subs can do the same job.

The Dolphin II's top speed maxes out at 20 knots when submerged. But the maximum distance before needing to be refueled is around 9,200 miles at a speed of eight knots underwater. This puts the submarines in range of Iran.

And that's why Israel is investing in an up-armed submarine fleet. The Israeli military wants to maintain its undeclared nuclear strike force. Given Israel's small size, a nuclear deterrent promises massive retaliation if Israel's homeland is threatened.

Plus, submarines are very useful for littoral operations off the Gaza Strip and Lebanon.

Israel has also boosted its submarines' operational tempo. In 2013, Israeli submarines spent 58 percent of their time at sea compared to 36 percent from 2010 to 2012, according to the Times of Israel. This not only included secretive missions off Lebanon, but "deployments lasting several weeks that took the submarines thousands of kilometers from Israel," the paper reported.

In July 2013, a series of mysterious explosions occurred at the Syrian port of Latakia. Though Israeli aircraft were likely responsible for the attack — which targeted a shipment of Russian Yakhont anti-ship missiles — such operations can be carried out by submarines.

Now the Israeli navy will soon have the much more capable way to do it.

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