Liquid hydrocarbons? You'll sink like a brick. I don't know exactly what methane and ethane do at minus whatever but the density is at least 30% lower than water...
So nothing you could swim in, but it would be relatively easy to build a boat.
Hmm, come to think of it: Titan's gravity is 0.138 g. So you might be able to stay afloat in liquid methane by actively swimming upwards, even if you can't float.
Similar to how birds stay afloat in the air, despite being heavier than air.
Wouldn’t it dissolve a lot of things, including space suit seals? If it wasn’t for the extreme cold embrittlement anyway.
Basically, you wouldn't want to build them out of materials that are useful at human room temperature, but you could perhaps build them out of materials that are liquid or even a gas on earth, but solid at Titan's temperatures. (No clue whether ethanol would be good, it solidifies at -114.1C, but I have no clue what kind of solid it would be.)