Bluebulb Projects' The Measure of Things presents:
30,000 is about 400 times the number of Submarines in the US Navy.
In other words, it's 420 times the count of Submarines in the US Navy, and the count of Submarines in the US Navy is 0.0024 times that amount.
(a.k.a. Subs) (includes all types, all classes) (2015 figures)