The Tailgater (and the Flex, same item for more universal use) is for solid ground only. Even at a marina if you put it on the boat or a bouncy floating dock it can drift in and out if it rocks at all as it tries to re-level itself. A full sized dish mounted on a Track-it is a bit more forgiving in this regard, and the big thing you pay extra for is it tracks while the boat swings and turns.
I used to be in the sat TV business, and was when we first bought the Hatteras. I too tried the Track-it route first and couldn't find a place where it wouldn't either get in the way, be obstructed at certain angles, or look really funky. They were extremely nice and helpful people to deal with and took my return of the unit with no issues (this was 7 years ago). What I probably should have got was one of the big KVH C3's but allowed myself to get talked into their at the time new, small dome units, an M2 which mounted very nicely on the arch. The downside it was nonHD , which we really didn't care about at the time,and Direct Tv only (we really would have preferred DISH and still do) and billed as an "anchor or dock" unit. We have almost zero occasion to want to watch TV while underway, but the thing worked perfectly fine while putting down a calm ICW; we liked the included satellite radio stations and I did watch some of a football game and some horse races . If you have a similar usage profile, you might be able to find one of these on e-Bay or a marine surplus store cheap.