This site contains some selected details on coastal traverses, sea level traversing and deep water soloing in Tasmania. It's under construction at the moment.
Here are some possible definitions. Don't be bound by definitions though: the idea is to have fun.
Coastal traversing. You need a piece of coast, with plenty of cliff going into the water. You can swim or climb, or walk or run if that is possible. But stay within reach of the water: walking along the top of cliffs is cheating. The idea is to have as much climbing as possible, and swim if things become unclimbable.
Sea Level Traversing. This is roughly the climbing part of the above. Sea level traverses are essentially climbs that go (roughly) sideways above water. Often they're done unroped.
Deep Water Soloing. This is basically climbing above water unroped. It's usually in an upward direction, as otherwise it would be called sea level traversing.
What I've called coastal traversing here is what for me evolved through a series of adventures with my brother Hamish over the 1990s and 2000s. This is not to say that we were the first to do what we did. We were mostly inspired by the relatively famous "Sea Level Traverse" at Freycinet Peninsula, which was first done (over 2 days) in the 1970s. That traverse would be called a "coastal traverse" according to the definitions above, although it is often done roped in sections. To me, coastal traversing is as much about place as it is about climbing.
The endurance factor is substantial in coastal traversing because many of the traverses are kilometres long and may involve many sections of swimming and exiting the water onto cliff.
All of these traverses are great fun adventures, but some are not as satisfactory as others in terms of their quality as an actual sea level traverse. This is mostly because they lack enough climbing. The Sisters Beach to Rocky Cape traverse contains quite a few short sections of climbing, but nothing that is very continuous; moreover only about 5% of the overall time involves climbing. On the other hand the brilliant Chasm Creek to Deep Glen Bay traverse involves extensive sections of climbing on many different rock types (mudstones, limestone, dolerite and granite), interspersed with some intimidating swims, all within an awesome setting.
Hamish Jackson on Dauntless Point.