StarSolidStarSolidStarHalfStarOutline(2.5 stars)

Filmmaker Liz Garbus has been busy lately, and a little all over the map, chalking up directing credits on last year’s political documentary “All In: The Fight for Democracy,” the violent season 4 finale of “The Handmaid’s Tale” this spring, and now an affectionate yet mostly clear-eyed portrait of Jacques-Yves Cousteau, the famed multi-hyphenate, who died in 1997. Cousteau was, as Garbus’s film notes, a sailor, undersea explorer, environmentalist, philosopher, inventor, scientist, researcher and filmmaker, winning three documentary Oscars, in 1957, 1960 and 1965.

But “Becoming Cousteau” also looks at the man behind these roles, which include the invention of the aqualung diving apparatus and hosting the hugely popular television series “The Undersea World of Jacques Cousteau,” which ran from 1968 to 1976. Cousteau was, by his own admission, a less-than-perfect husband and father, choosing the sea over his family — meaning, in this case, wife Simone, and sons Philippe and Jean-Michel. After the 1990 death of Simone, it was revealed that Cousteau had a longtime secret mistress, some 30 years his junior: Francine Triplet, with whom he had fathered two children (Diane and Pierre-Yves) and whom he married at 81, a scant six months after Simone’s death.

“Becoming Cousteau” is not a tell-all, though. In fact, it could use a little more scrutiny into, for example, how its subject reconciled his ecology-minded public stance with the decision to accept funding for his voyages on his beloved vessel the Calypso from oil companies that hired him to conduct underwater research on potential drilling sites.

That arrangement is mentioned but glossed over.

Otherwise, “Cousteau” is a thorough if somewhat by-the-book profile of a pioneer in the field of marine ecology and an activist for better environmental stewardship. If it sounds like a wake-up call about a rapidly warming planet, the alarm bell it rings is a necessary if at times overly sober-minded one.

PG-13. At area theaters. Contains some strong language, images of brutality against sharks, a disturbing diving accident and smoking. In French and English with some subtitles. 93 minutes.