Lozman v. The City of Riviera Beach, Florida
http://www.ca11.uscourts.gov/opinions/ops/201010695.pdf
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Interesting. This decision indicates that there is a federal definition of
'vessel' that supersedes and doesn't take into consideration the Florida
statutory definition of 'houseboat'.

It doesn't say this and it also doesn't indicate this.

In connection with the, What's a 'vessel'? question, it ruled merely
that, for the purposes of the case, that is, that 'the point' at issue
in this respect was merely whether for the purpose of determining what
may be the subject of federal admiralty jurisdiction in a foreclosure
of a maritime lien proceeding in admiralty, the federal law definition
of 'vessel' and not what states variously may adopt and use for their
state law purposes governs. Hardly interesting and not novel.

If this is true then the State of
Florida mandating a particular type of MSD for a 'houseboat' as opposed to
a 'vessel' is flawed.

This is a state law issue enforceable by the state as a matter of
state law and does not implicate federal court admiralty jurisdiction
in a maritime lien foreclosure proceeding prosecuted under federal
maritime law.