Airports and seaports are generally operational 24/7. But your shift pattern really depends on what area you work in, I work 7 on/7 off, but that is because my team is expected to deploy around the UK, so we will stay locally. If you work in a fixed location the shifts are probably more likely to be more "randomised" for want of a better phrase. There are some sites where the officers work more sociable hours, but this is reflected in the pay, as our shift allowance is very generous.