As an engineer, Peter Robbins was fascinated by the precision of Germany’s U-boat technology during the Second World War.

As an entrepreneur, he was intrigued by the prospect of deep-sea tourism.

In response to both urges, Robbins set out to design and build the Alicia, a one-of-a-kind, six-person sub with a panoramic view for all on board.

A new “NOVA” presentation follows him on his four-year voyage to create from scratch such an underwater vessel, then use it to explore the sunken wrecks of German U-boats.

Assembled from 2 million parts at a cost of $1.5 million, Alicia is an 18-ton craft that can dive to 1,000 feet. And it’s a monumentally complicated project, whose construction required shopping for seats at a business supply store and the creation of an innovative acrylic dome that offers a 180-degree view of the ocean realm.

The film traces Alicia’s progress from design to manufacture, then its launch from England’s Plymouth Harbour in search of the U-boats that litter the seabed of the English Channel. And joining Robbins on this maiden trip: Rudi Wieser, a U-boat veteran who survived the wartime demise of his own submarine more than 60 years ago, and now, at 81, hopes to catch another glimpse of U-1195.

“NOVA: Underwater Dream Machine” airs at 9 p.m. on Tuesday on PBS (check local listings).

Other shows this week to look out for:

l It’s an unlikely place for the debate over illegal immigration to be raging: the Colorado Rockies. But that’s where Tom Brokaw headed for “In the Shadow of the American Dream” , a one-hour special airing at 9 p.m. on Tuesday on NBC. This pristine stretch between Aspen and Vail, with its historically white population, has seen an influx of thousands of Hispanics, mostly from Mexico. Drawn to jobs in the construction field, they are also filling the schools, churches and medical clinics. During an eight-month investigation, “Tom Brokaw Reports” takes viewers behind the scenes to reveal a story of illegal immigration.

l With more than 700,000 children of military families under the age of 5 separated from their mother or father this holiday season, “When Parents are Deployed” addresses the challenges these families are facing. Produced by Sesame Workshop, the half-hour special shares candid and intimate moments from the parents and caregivers affected by deployment. And it hears from kids as they express how they cope with the daily stress and fears associated with the absence of a military parent. The special supplements an educational outreach program called “Talk, Listen, Connect: Helping Families During Military Deployment,” with a kit available online at www.sesameworkshop.org/tlc. With Oscar-winning actor Oscar Gooding, Jr., as host, “When Parents are Deployed” airs 9 p.m. Wednesday on PBS.

[bul] Oh, boy! Here’s a holiday treat for fans of “My Boys,” TBS’ new comedy series: Five fresh episodes will air Tuesday through Thursday! The network’s first-ever scripted comedy, “My Boys” stars Jordana Spiro as a twentysomething gal who’s happily one of the guys, savouring the joys of weekly poker games, pub-hopping, sports and sassy banter with her fraternal chums — even as she ventures out on the occasional search for romance. New episodes air Tuesday and Wednesday at 11 and 11.30 p.m.