Long before high-definition cameras and the global reach of natural history television, French adventurer Jacques Cousteau introduced viewers to a world few had ever seen.

The Undersea World of Jacques Cousteau, first broadcast between 1968 and 1976, remains one of the defining documentary series of the television age.

It was not simply a programme about marine life but rather an adventure series, a chronicle of exploration and, at times, a carefully constructed mythology centred on one man, his ship and his crew.

For modern audiences, the series can initially feel dated, for the camerawork is at times rough, the narration occasionally melodramatic and the editing often favours atmosphere over scientific detail, yet those qualities are in fact part of its appeal.

The marvellous vessel, The Calypso, was itself central to the programme’s success.

An old minesweeper from the war, she was lovingly converted and donated by Loël Guinness as a philanthropic gesture to Couestau and his crew.

She became one of television’s most recognisable ships, a floating base from which Cousteau and his team ventured into waters that still felt remote and mysterious.

Her fame extended far beyond the series, with John Denver’s eponymous song having transformed the vessel into a symbol of exploration and environmental awareness, celebrating both the ship and the mission it represented.

The structure of the series is deceptively simple; one week they are tracking whales off California, the next they are exploring the Galapagos Islands, diving beneath Antarctic ice or investigating shipwrecks in the Pacific.

The destinations alone gave the programme much of its appeal, at a time when international travel remained inaccessible to many viewers, Cousteau brought distant worlds directly into people’s living rooms.

What distinguished the series was its sense of discovery; the oceans were presented not as environments under immediate threat but as vast frontiers still waiting to be understood.

Early Cousteau productions reflected attitudes towards wildlife that would be somewhat unpalatable by today’s standards, and admittedly some aspects of the show have aged rather poorly.

Sharks were sometimes treated as threats to be subdued rather than animals to be understood.

These moments stand in stark contrast to Cousteau’s later evolution into one of the world’s most influential environmentalists and advocates for marine conservation.

Yet it would be unfair to judge the series solely through a modern lens, as The Undersea World belongs to a period when underwater exploration itself was still pioneering.

Cousteau helped develop technologies that made much of this work possible and brought public attention to ecosystems that were largely unknown outside scientific circles.

The programme’s greatest achievement lies in its ability to communicate wonder.

Beneath the iconic red woollen cap, the cigarette smoke and the occasionally theatrical narration was a genuine fascination with the briny blue and its inhabitants.

Many have followed in Cousteau’s wake, yet few have matched the combination of exploration, personality and discovery that defined his programme.