I remember that when I visited Yugoslavia, people were supposed to speak Serbo-Croatian. Now, they speak Serb, or Croatian, or Bosnian, apparently. However, the funny thing is that, among the various Serbo-Croatian dialects, they all picked the same as the basis for their new fangled national languages : Shtokavian ( Shtokavian - Wikipedia ). So I can only assume that all these “national” languages are more similar to each other than the different dialects within any of these countries are.
I speak American. 
One sentence, 1.05 languages:
“Bread, butter and green cheese is good English and good Fries” (Fries here, meaning Frisian, is pronounced ‘freese’)
“Brea, bûter en griene tsiis is goed Ingelsk en goed Frysk”
I heard some Frisian spoken in the Netherlands on a long-ago trip to said nation to visit some cousins at the ancestral Merkotijn manor. Hauntingly familiar but not readily comprehensible to me.
Isn’t Scots closer than Frisian?
Here’s a chunk:
I can read this, but every so often, it just veers off the rails and looks incomprehensible. I suspect that listening to it would be clearer.
Which dialect? 
Well, isn’t that the trick?
Back to English for a second…
What about more obscure dialects. Even with modern telecom, dropping someone from the Ozarks or central Appalachia into, say Tasmania or rural Wales might just meet some level of incomprehensability.
That’s fun and all, but I challenge any English speaker who hasn’t studied those languages to pick up a newspaper in Dutch or Fries and make sense out of an article. Here’s one in Dutch:
Something happened in or near Croatia (I assume) or Dublin or Germany with some sort of transport (189 passengers) and there was blood involved. OK: 189 Irish-Croats were traveling in Germany and someone started bleeding. Or something. 
That’s all I got. I tried not to cheat by using my (limited) knowledge of German. Speaking of which, Dutch and German form a dialect continuum. Low German (Plattdütsch) is quite similar to Dutch.
Linguists seem to be arguing over whether Scots (as opposed to Scottish gaelic) is a dialect or a whole 'nuther language. Frisian is accepted as a language.
I admit I do find the debate over which is closer to english, Scots or Frisian, to be quite fascinating.
You get no argument from me. Change the Frisian sentence a bit and you get something confusing to me:
“Bûter, brea en griene tsiis; wa’t dat net sizze kin is gjin oprjochte Fries” 
("Butter, bread and green cheese, whoever can’t say that is no genuine Fries).
A lot of people confuse the Scandinavian peoples with the Baltic peoples. They are completely different. The indigenous peoples of the Baltic region have been influenced by Arctic peoples. They share both genetic ancestry and language etymology with northern Eurasian tribes - as do the Hungarians. The Scandinavians don’t have this.
Also noteworthy about the Frisian language: You’ve got your West Frisian (in the Netherlands), your East (Or Saterland) Frisian in a tiny spot of northwestern Germany) , and your North Frisian (Northern Germany on the west coast) dialects. All 3 dialects are considered to be mutually unintelligible to each other.
Well, for what it’s worth, I’m a native German and can figure out written Dutch quite well and spoken Dutch good enough to be able to help in road navigation and such, simple conversations. Probably it helps that my second language ist English. I’m at least better at figuring out Dutch than Palatine (which is spoken in my home country not far away from where I live) or Swiss German.
And the Scandinavian point of view heard from.
FWIW, here is my experience. A friend of mine from Georgia (US) and I from Philly were having dinner with a Serbian who spoke excellent English. My friend asked him how different were Serbian and Croatian. He replied that the difference was less than between the two of us. He added that they were trying make the difference greater was not to much effect.
A colleague of mine who left Germany at age 16 spent a year in Zurich and said that by the end of the year he was just beginning to understand Schwyzertuusch (Swiss German). I am not sure to what extend Plattdeutsch and Hochdeutsch are mutually comprehensible, but it would not at all surprise me if speakers of Platt could understand Dutch.
I have visited Barbados 17 times for two or three weeks each time and I cannot make anything of the native variety of English, although they understand me perfectly and can crank up a good facsimile of American English. This really is a distinct language, possibly as different as Swiss and standard German. I have twice run into Cockneys I simply could not understand. I once met a highland Scot who spoke beautiful English, but then gave a sample of his native dialect (of English, not Gaelic) which was incomprensible.
Finally, I will mention a detective story I once read (in English translation) by the Swedish pair Per Wahloo and Maj Sjowall. The murder took place in Malmo and the perp had escaped to Copenhagen. As a result the head of the Swedish and Danish police had to collaborate. According to the story, although they had known each other well, in this case when they had something substantive to discuss, they gave up the pretense that each understood the other’s language and settled comfortably into English. I did know a Norwegian who married a Swede and they each understood the other’s language well enough that each spoke their native language. I assume their kid just learned Mommy’s language and Daddy’s language.
When I did “cheat” using a little bit of German, I had something happening to the people’s “stupid ears”. Sometimes “bloed” is just blood after all.
Perhaps there was a time when these foods fit a Frisian stereotype of some kind.
My brave/stupid attempt; I made everything over-literal to show where I think the words came from; (…) means I added something, [?] means a word I don’t understand, and I hyphenated some things to show Dutch compound words that aren’t compounds in English. I’m guessing “daalde/dalt” is something about descending or landing because otherwise the story makes no sense.
Ryanair flight [?] so fast that passengers out ears bleed: “I thought that my end nearby was”
One Ryanair flight from-out Dublin is not [?] [?] so-as planned: the plane [?] 189 passengers near the Croatian bath-place Zadar [?] [?], [?] by one need-landing (i.e. emergency landing) in Germany so fast that some passengers out the ears bled.
On the Slavic languages: my mother was a linguist, who specialized in them, and spoke virtually all of them with different degrees of fluency. Slovak was her first language, and she was qualified to teach Russian, Czech, and Slovak. She could read Old Church Slavonic as well.
Anyway, according to her, Czech and Slovak blurred the line between being separate languages, or just dialects of one language. This was because of an historical period when the Germans had controlled Czech area, and had tried to suppress it. It was revived eventually, but it made greater differences in the two languages than there otherwise might have been. THEN, the two language speaking areas got mashed together into Czechoslovakia (a word my mother made me learn to spell when I was 7), with no borders between the areas, and this promoted a closeness between the two languages. Basically, a Czech could speak Czech to a Slovak, and the Slovak could answer in Slovak, and they’d understand just fine, kind of like when people in the US from different regions speak very different dialects, but understand each other.
All Slavs pretty much had to study Russian in school from about 1920 to 1990. Anyone who grew up in that time probably did not become fluent in Russian, but absorbed quite a lot of passive knowledge, and can therefore understand a Russian movie. It helps that the languages are similar, but it’s the reason there is no reciprocation from Russians.
On another subject: American Sign Language and** French Sign Language **are very close, that they are mutually intelligible as long as you stick to simple subjects. I had a conversation in DC with some people, and I was having a little trouble following them, and then they said they were French. Now they had been visiting their daughter at Gallaudet for over a week, so they’d picked up some ASL, and I know French, so I could fingerspell words in French, but after that was cleared up, we went on to have a long conversation, and it was quite rewarding. It was mostly about how they liked DC, and what their daughter was doing, and my background in sign-- how I worked as an interpreter, and so forth. It was very interesting.
I have had exchanges with Deaf people in other countries. It is possible to have very basic “I’m from American”; “Where’s the bathroom?”; “Is this restaurant good?” exchanges with Deaf people even without a mutually intelligible signed language, but with ASL & LSF, much more is possible.
Of course, ASL (and presumably FSL) is much more “onomatopoeic” than audible languages, and that’s going to help inter-intelligibility a lot. In fact, even without knowledge of a formal sign language, humans from different cultures will often understand a lot of each others’ gestures.
I happen to work with several people whose native language is Spanish and several others whose native language is Italian. They claim they can understand each other without too much difficulty when speaking those languages.
I also recall being in the Netherlands and looking at signs and get a pretty good sense of what some of them were saying. I had a Dutch person say it is pretty easy for them to understand spoken American English even if they haven’t studied it.