VDSOWMen's Waterproof Sport Watch with Alarm/Stopwatch, Large Wrist Military with LED Backlight, Black, S, Strap, Black, S, Strap

How do you set to 24 hour mode please?

How do you actually switch it on? Mine has turned up today, I've pressed every single button but its not working, nothing on the screen whatsoever?

Can this watch be used whilst swimming?

How long will the battery last