A slight variation on Jack's answer. I think the word 'tugs' could be used here instead of 'navigation'. It's a clearer expression of what kind of vessels are involved.
http://www.artanderson.com/workboatdesign.html

I did not know this dictionary, and I'll check it out!

I must say that all this information is readily available on the Internet if you are at least slightly familiar with the terminology involved.