I have two things to say about this case. Both of which may principally be of interest to those readers down here in San Diego.
First, did you realize that you're subject to admiralty jurisdiction when you're hanging out at Mission Bay? You apparently are. (For those not familiar with Mission Bay, it's essentially a recreational playground that's used somewhat like a large pool. Not something you'd especially think was a navigable waterway or would in any way be governed by admiralty law. But it is.)
Second, more broadly, I wonder whether this case isn't a perfect test case for the validity of Oliver Wendell Holmes' maxim "The life of the law is experience, not logic." Judge Rymer writes the opinion here, and as a matter of pure reasoning, I think her arguments largely make sense. Mission Bay ebbs and flows with the tide, and there's at least the potential for an impact on "navigation" broadly defined.
But none of the members of the panel live in San Diego, and perhaps none of them have ever been to Mission Bay. This stands in sharp contrast to both the district court judge -- Judge Miller -- and the undersigned, who lives within (figurative) spitting distance of the area in question. If you've actually been there, and know what it's about and how it's used, it's much harder to come to the conclusion that the area used for jet skiing here is really under admiralty jurisdiction. Which, I think at least in part, is why Judge Miller came to a contrary conclusion than the panel. That, I might add, plus the potential injustice of having admiralty law govern what would ordinarily be a routine negligence claim; here, the defendant is trying use admiralty law to preempt a state law tort claim and limit their liability to the $6,005 value of the Jet Ski under the Shipowners Limitation of Liability Act -- an Act that almost assuredly did not contemplate governing situation like those here.
When I say this is a good test case for the maxim, I don't think it strongly falls on one side or the other. But I do think there are competing perspectives here, and that those divergent views explain in large part why the district and appellate courts diverge on this one. So definitely something to think about.