The AQ-S820W-5AV is Casio’s answer to those who want G-Shock functionality in a slimmer, more lightweight package (only 46g). The "5AV" designation refers to its earthy khaki/brown resin strap and black bezel, giving it a distinct military or "field" look. While it utilizes a resin crystal to keep costs down, the recessed dial design provides natural protection against scratches, making it one of the best value-for-money "all-rounder" watches on the market today.

• Power Saving Function:: To preserve energy, the watch automatically enters a "sleep mode" where the LCD goes blank if left in the dark for an extended period, waking up instantly when exposed to light or when a button is pressed.
• 5 Daily Alarms:: You can set five independent alarms to stay on schedule throughout the day, along with an optional hourly time signal to keep track of passing time.
• LED Backlight with Afterglow:: The digital LCD at the 6 o'clock position features a dedicated amber LED light. You can customize the duration (1.5 or 3 seconds), ensuring visibility in total darkness.
• 100-Meter Water Resistance:: With a 10-bar rating, this model is built for more than just surface splashes. It is suitable for swimming, snorkeling, and heavy rain, making it a reliable companion for outdoor adventures.
• Dual Countdown Interval Timers:: Unlike standard watches with one timer, this model features two countdown timers that can be used for interval training (e.g., alternating between high and low intensity). These can repeat up to 10 times automatically.