Going by the gate system, it seems that it is the IJN light cruiser Tatsuta, with additions for the shipgirl herself. So it should be able to function as a boat, if not a warship.
So wait, does it still work, can it be used like a normal ship without her in it?
I'm guessing that shipgirls are more effective in combat because the vessel is controlled by a single mind, as opposed to many crewmembers that can work at cross-purposes, fail to communicate, mutiny, etc. In principle, perhaps you could sail the vessel into combat with a conventional crew, but only a foolish or desperate admiral would do so if they could deploy a shipgirl instead.
In this case, it's moot - Tatsuta's hull is apparently being used as a museum/park of sorts. Though it'd be awesome if, later on in the series, there were an emergency where the port was attacked and the vessel needed to be crewed in the traditional way and sent into battle in desperation - perhaps with Tatsuta as its captain (who better?).
Wow... This is Tatsuta-san's... so it's like this...!
TATSUTA BRILLIANT PARK
OPEN
Eeee! Why are you saying such embarrassing thiiiiiings!Inside Tatsuta-san... It's so warm nui.Hey, hey! Look over here! ...Whoa, it's really different from mine, ain't it?She had a favorable reception as a commemorative ship.