What does “Aquanaut” mean?

The Aquanaut is Patek Philippe's more casual sports line, introduced in 1997. It shares the rounded octagonal case shape of the Nautilus but has a dial embossed with a raised, grid-like pattern and is usually worn on a composite 'Tropical' strap designed to handle heat and water. The 5167A, in steel with a black dial, introduced in 2007 at 40 mm, is the reference most dealers think of first.

Like the Nautilus, the steel Aquanaut has been hard to buy new and has often traded above retail. The strap is part of the value: an original Patek Philippe strap in good condition, the folding clasp and the complete set all matter, and many owners keep a spare strap. The range also includes precious-metal, travel time, chronograph and ladies' models, so confirm the full reference and dial colour. Special dial colours and limited editions can trade very differently from the standard black 5167A.

Example: 'Aquanaut 5167A, black dial, 2020, full set, original strap plus a spare.'