Silent Hunter III is probably a much more obvious and, shall we say, not overwhelming transition from Enigma.
Since it's World War II, the technology and tactics will be more rudimentary and easier to learn even at high realism levels. Compare your familiar Lock On with IL-2 - which one would you find easier to get into right away? I think IL-2 would clearly be the answer there...
And it's by far the best-looking naval sim on the market, period.
Dangerous Waters - I intend to give it a shot myself shortly, but expect a sharp learning curve and lots of technical information to internalize. If you're fine with that - multi-platform goodness that's great for multiplayer.