Hints for ships and submarines?

[Evanitis]

Sea... the Final Frontier... to boldly go to the exact opposite direction sane kerbonauts usually aim for...

 

...but I don't have a clue how to start. My ship-prototypes tend to sink, while my test-submarines float happily. Both have a tendency to break apart when I get them into water. Ok, I heard that filled ore tanks are good for ballast, but that's the end of my expertise. What to use for propulsion? And for steering? Some smart way to get to water without hyperediting? Is there a way to EVA down there? I'm looking for vague, general advice here. I'm mainly interested in stock-solutions, but I don't mind a few targeted mods either if it's needed for certain tasks.

So... how should a spacelubber start to conquer the waters of Kerbin?

[Geschosskopf]

First off, if you want to play with boats and subs, do yourself a favor and get the Vessel Placer mod.  Then you can just dunk your stuff in the water with minimal wasted time.

Anyway, boats are relatively easy.  Most parts in KSP still float, just don't load them down with scads of engins and I-beams and you'll be OK.  For propulsion, use jet engines.  You do, however, need a fair amount of thrust to travel at any speed.  Steering is done by normal control surfiaces which can be in the air or in the water.  The main trouble with boats is that parts that if at some point are completely out of the water ever touch the water again, the games checks to see if they break.  This puts a real cap on survivable speed because boats plane up as they accelerate, lifting the bow.  If the bow part ever gets clear of the water, it will likely break when you slow down and it touches water again.

As for subs, I recommend one of several mods for them.  Ore sucks for ballast because you can't get any more of it once in the water (which is hard-coded to have zero so you can't drill the sea bottom).  Thus, releasing ore ballast is a 1-time thing with a 1-way trip to the surface.  It's only really useful for submersibles like the real Trieste that basically go straight down and straight back up.