The phrase "that sucks" or the longer expression "that sucks mud" really has very little to do with sexual connotations the way so many seem to think, the link only being inferred after the event by those who guess and are not familiar with US Navy terms of years gone by.
It's originally a US Navy term, I believe from the Korean war. A type of river boat was used in shallow rivers that used an impeller rather than a propeller, sucking the water in and blowing it out the aft of the boat, not too much unlike personal watercraft (PWC) do today (i.e. Seadoos). If the water became really too shallow even for these boats they sucked mud instead of water, hence the phrase "she's sucking mud" or "she/ it sucks". I don't know, but I can guess that even PWC today have this problem with sucking mud in the wrong type of water.
You see a great example of this direct use in Star Trek TOS when the comment is made "bring her up Scottie she's beginning to suck mud!" Gene Rodenberry was very familiar with US nautical terms.