I didn't know there were people that ever raised their own ships
Yeah, as much as possible, I let the vassals eat the cost of maintaining fleets. But, I also generally use an individual fleet only for a few months.
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Speaking (as some comments above were) of development in coastal provinces, consider personally holding a city in your capital county (if it is coastal).
- Cons: the "Wrong Holding Type" malus, meaning that the revenue generated by the city is halved *and* its garrison will not reinforce (making it very vulnerable to siege once the castle(s) and temples(s) prior to it have been sieged-down);
- Pros: you get *all* the final total of revenue generated by the city; so, with a well developed market *and* port (and even moreso if there is a trade center in the county), this is still going to be more gold than your capital castle generates. BTW, the "Collect Taxes" steward action applies to a city *if* you personally hold it.
- Conclusion: You trade the possibility of raising levees from one holding in your demesne for increased revenue from it -- but, raising levees is episodic, whereas collecting taxes is on-going.
== In a game using the CK2+ mod ==
Testing this idea, at a still moderate level of development in both the capital castle and a city I hold (and with a trade center in the county), I'm getting 10%+ more income from the city than the castle.
By way of comparison, with "Highly Tax Oriented Burgher Focus" and "Low Burgher Obligations", the revenue I'm receiving from the city I personally hold is a bit more than 3x the revenue I'm receiving from an identically developed mayor-controlled city in the same county.