This is a watch designed for under water diving. It can be analog or digital; but it has very stringent feature requirements. Aside from being water resistant, a dive watch is expected to have other features such as:

The standards and features for diver’s watches are regulated by the International Organization for Standardization in the ISO 6425 standard. For all their sophisticated functions, however, recent advancements in dive technology have relinquished dive watches to the role of redundancy. For many divers, they’re a handy double check of what the console on their regulator is already telling them.

• Adequate readability/visibility at 25 cm (9.84 in) in total darkness.
• The presence of clearly distinguishable minute markings on the watch face.
• Magnetic resistance
• Shock resistance
• Chemical resistance
• Strap/band solidity
• The presence of an End Of Life (EOL) indicator on battery powered watches.