I think your best bet is to install the official patch which, among others, adresses that bug.
Download it (here) and install it.
If you don't want to download that patch, then try the console workaround. I'll try to explain it short and sweet:
As far as I've seen, you started the game with the -console added and the console appeared. Close it by clicking X in the upper right corner of it. Now you get the normal game menu. Reload your last save and play until you need to escape Society of Leopold.
Get near the boat, the best way is to stand on the edge of the pier, by the boat, but do not enter the boat. Press Esc on keyboard (so it will be easier to return from console). Then open the console by pressing the key left of "1"-key and above "TAB"-key on your keyboard (whatever it is marked).
Now, as Intergalactic says:
A console will open. Type:
SaveJohansen() (press enter)
changelevel2 la_hub_1 taxi_landmark (press enter)
( Or as Nosferatu: changelevel2 la_hub_1 sewer_map_landmark )
Take care to get the capital letters right. If you get an "not defined" error
you probably messed up with the spelling.
Now close the console again and return to game. If you have some mobility or inventory problems afterwards, check the above mentioned thread again for tips. Otherwise, enjoy the game!
I hope this was helpful.