Just my two cents: regular hose clamps generally work fine as long as they're not right near or submerged in saltwater. I've also used those plastic clamps suggested by Weasel1960 but I've frequently had bad luck with their sizing given that tube outer diameters seem to vary a lot. Anyway, for anything submerged or in danger of getting splashed, I just use plain old zip ties (cinched tight with help of pliers) most of the time. However, they don't work however on braided or super thick tubing so use the plastic clamps for that. Also, the zip ties are one-time use. Once on, you have to snip them off if you want to remove.