Too late for that now anyway. By the way, 7185 khz would be 7.185 mhz, and you would need Single Sideband capability to hear it, otherwise it would all sound very garbled and unintelligble. That's probably one of the freqs the Goddard Space Flight Center ham club WA3NAN is using. It's based in Greenbelt.
As for things like tugboats and such, the marine channels are where you want to be - and unlike those milair and other frequencies you were trying in the Nat Guard thread, these are well within your range. The marine frequencies, and the respective channel numbers are all in the wiki lined up right
here You have a Service Search for the marine band.
That little antenna that comes with most handhelds is often referred to as a 'duckie' and is only really useful for very local stuff - it's quite lossy at many frequencies. You'll have to be more specific about how you are using the 528 - in a car, in the house, portable, ect so folks can recommend an antenna that will perform better than that lossy little pig. That is going to make a big difference in what you can/can't hear.
I will say that I would hesitate before putting a big outdoor antenna on the 528. You see, handhelds are made to work with the relatively low level of signal that a duckie (or similar) would deliver. Anything more than that, and you may start hearing pagers and other junk where it doesn't belong. In extreme cases, the 528 would lose sensitivity on one or more bands (a very loose description of what we refer to as 'desense'). Filters are available to fight this kind of interference, but where possible, the correct selection of an antenna (and associated coax) will help minimize those kinds of problems, particularly in our area.
73s Mike