IanD

Flexible solar panels are more than 5x as expensive as rigid ones for the same output, which is why most boaters use rigid. They also have a reputation for having short lifetime unless carefully/professionally/expensively installed. Flexible ones can look a lot better but you really pay a lot of money for this.

The same choice as for many other bits of kit such as inverters -- you can pay more for stuff supplied and supported (including spares) by companies like Evo/Webby, or buy something considerably cheaper from a less reliable supplier. The kit might or might not be as well designed and made -- it may be made in the same factories, or almost identical -- but is more likely to have issues with spares and support/maintenance in future. You might get a good one which is reliable, or one which turns out to be junk that breaks down and is essentially unfixable -- but you'll have saved a lot of money up front. Literally, you pays your money and you takes your choice... 😉 (N.B. "I bought a cheap Chinese one and it was fine" is anecdote not evidence, just like "I didn't wear a mask and I didn't catch Covid" -- you need to get a lot of them out there to know if they really *are* good or bad...)

And there are lots of debates about whether the Titanic steel was brittle at cold water temperatures, whether the rivet material was bad and so on. But to answer the OPs question, the hull of a narrowboat made from 6mm plate is a *lot* stronger than that of a typical ship (or the Titanic), to be similar it would need about 2.5mm plate. Which is why narrowboats are robust, even when bashed into things harder than icebergs... 😉

Oops, misread cm for inches and then did the conversion... 😞 1" amidships seems to be the accepted figure, so that's equivalent to 2.5mm for a narrowboat. Explains a lot....

Stiffness/strength of a panel -- like a hull -- goes up as the square of thickness, but mass/hull forces in a collision go up with the cube of size. So if you scaled up a narrowboat 10x in all dimensions to a ship 700' long and 70' wide drawing 20' or water weighing about 20000 tons, the hull would need to be built from 60mm plate to be as strong as a narrowboat built from 6mm plate. Still wouldn't make it impossible to hole, but difficult. The hull of the Titanic (roughly the size above) was built with 48mm plate...

It's a cooling and heating unit, the heat pump connections just get swapped over -- the heating is "free" with the aircon (or vice versa). All heat pumps units like this -- ground source home ones included -- use a secondary liquid cooling loop as well as the primary HFC one, the heat then has to be transferred from this to the environment somehow. The ground source ones use a network of brine-filled pipes, which you could then take to a skin tank. This unit is designed to use fresh water directly, hence the 5C intake limit.

The marine aircon/heating heat pumps don't work with inlet water temperatures below 5C, they shut down -- I looked at using this one for a narrowboat. https://www.advanceyacht.co.uk/marine-air-conditioning-units-all/p/frigomar-scu16vfd So you need another source of heating for when the water is cooler than this, for example a diesel heater or stove.

As was pointed out, loaded trad boats didn't have much freeboard when loaded, but also drew a lot of water (up to 3'6" or more). Tugs designed to pull them were heavily ballasted so they also sat quite deep in the water to allow them to use a large diameter propeller for best pulling power. Most modern boats draw much less than either because poorly dredged canals today mean a deep-draughted boat can have difficulties getting around some canals, but since the internal height still needs to be tall enough for people they sit less deeply in the water, usually not much more than 2' draught though some are deeper -- so a lot more of the hull sticks out of the water, they look more like a lightly-loaded trad boat. Modern tug-style boats which are high out of the water look wrong (because in the old days tugs didn't have much freeboard) so they're often more heavily ballasted than non-tug-style boats which means they draw more water. Look "sleeker" and lower -- a bit like a sports car -- but can be a bit less practical because of this (also like a sports car)...

The newest Eberspacher is said to be quieter than the old ones, and can throttle down to well below full power (1.3kW?) to reduce cycling if you don't have all the radiators on.