Each block is built on a 3x3 grid. We cropped the letter-forms to their absolute maximum, while still legible they take on an abstract form matching beautifully with the geometric shapes of the flags.

And just in cast you were wondering what the flags mean:  
J - I am on fire and have dangerous cargo aboard
O - Man overboard
S - My engines are going full speed astern
H - I have a pilot on board