Ok, so lets say to board a cruise ship it would usually take $60$ to $90$ minutes.
Now it takes only $10$ minutes.
In percentages this is:
$60-10 = \frac{50}{60} = 83.3\%$ reduction (ie. from $60$ minutes to $10$)
$90-10 = \frac{80}{90} = 88.8\%$ reduction (ie. from $90$ minutes to $10$)
Is this correct? For some reason I feel that this is wrong.... and its driving me crazy
"$60-90$ minutes to $10$ minutes is a reduction of $83\%-88\%$ of time it used to take to board a ship."
How can a $30$ minute difference be only just $5\%$ different?
It's correct - the smaller is final time, the smaller is percentage difference. For example, if time now is 60 minutes, we have $0\%$ decrease from 60 minutes, but $33\%$ decrease from 90 minutes. It, at other hand, new time is almost zero, then decrease from either 60 or 90 minutes is almost $100\%$.
What is constant (independent of new time) is ratio of percents left (=what percent is new time of any of old). For example, if new time is 60 - it's $100\%$ of 60 but only $67\%$ of 90 - so ration is 3:2. In your case, it's $\sim 16\%$ vs $\sim 11\%$ - again 3:2.