It's actually much worse than that. At sea, those with operational responsibilities don't work a normal day or week. Not only are you working over 100 hours, but you destroy your circadian rhythm. While it shows 23 hours of sleep in every 72, that's under optimal conditions when things aren't breaking and operations / drills aren't interrupting everything. This is what my full 72 hour rotation looked like in 5 on / 10 off:

DAY 1:

0600: Wake up, shower/shave, breakfast, make rounds to Engineering and Combat to get situational updates, head to bridge for turnover.

0700-1200: Watch

1200-1300: Lunch, maybe some personal time

1300-1700: Work, maybe catch a nap for an hour (1)

1700-1800: Dinner, or skip it for a workout

1800-1900: Intel Brief

1900-2100: Work, personal time, or nap

2100-2200: Coffee, round for watch, get to bridge early to adjust eyes

2200-0200: Watch

DAY 2:

0200-0700: Sleep (5)

0700-0800: Breakfast

0800-1100: Work

1100-1200: Lunch and rounds

1200-1700: Watch

1700-1800: Dinner

1800-1900: Intel brief

1900-0100: Sleep (6)

DAY 3:

0100-0200: Coffee, rounds, more coffee, turnover

0200-0700: Watch

0700-0800: Breakfast

0800-1200: Work, maybe nap (3)

1200-1300: Lunch

1300-1600: Work

1600-1700: Dinner, turnover

1700-2200: Watch

2200-0600: Sleep (8)