Thinking about seasteading and how it relates to agorism (I did a post that barely touched on this a while back, in response to Patri Friedman) again, I think what I see what my intuitive objection is to the current seasteading model. It seems to me that the current "seasteading" approach seems to be modeled on the currently existing nation state. And indeed, most seasteading proponents seem to be at least quasi-statist in their thinking. Certainly they don't strike me as a bunch of hard core anarchists.
A more anarchist/agorist approach to seasteading to me would be a colony of small ships, essentially houseboats but maybe with a bit more range, who trade goods and services amongst each other outside of the purview of any sort of governing body at all. One of the major advantages of this approach, to me, outside of the obvious one that you don't need millions and millions of dollars to get started, is that you also don't provide an obvious, centralized target for government reprisal. This means that you don't have to be as autarchic. If you need to pick up some land-based goods, well, you appear to be just a person with a houseboat coming in to shore to restock/refuel... completely inobtrusive for the most part.