I use a "happy Wanderer" its not omnidirectional. but it also works, I have not had any luck with omni's they need a strong signal to compensate for their poor performance.
I can confirm that. OMNI is usually with build in ampl. / you have to find the way to supply it/ but digital TV need stronger signal than analog. Medium YAGI antena is way to go.
I have used mine for about 3 years, it means that you do need to adjust the direction and its a pain whilst on anchor. But in the marina / jetty its great and it is pretty much built to last. You could build a similar one yourself to try it out. Its basically made from plastic conduit about 1 meter long with a "T" piece that feeds (and splits) the 2 wires from the antenna cable. Its probably called a Dipole. Others with Omnis are usually very jealous of the signal we get. oh! and no power amp required.