Funny story: I was in Spain several years ago and was talking to a guy I met about sailboats. I mentioned I had a boat, and he asked how big. I thought for a second and said "7 meters" so as not to be an ignorant American. He thought for a second and said "huh, 21 feet".
I'm not sure what the situation is in other European countries, but in the UK we use different units depending on the use so most people are use to working with both imperial and metric.
Perhaps with the exception of fahrenheit most people here will know what you mean if you use units like feet and will often even prefer thinking in feet over metres for certain things. Personally I default to feet for something like height or a floorplan, although I can think in metres quite easily too.
…which is why the French Navy (who originally defined the unit) switched it to be SI derived in 1906 and the international standard was updated in 1929.
And knots. Speed limits at sea in Norway (in harbours and other places with much traffic and little room for maneuvering) are always in knots. But we measure water depth in meters, not fathoms.
Funnily enough, about ~15 years ago TVs were still in cm, but somehow when flat screens came along (and people generally bought much bigger TVs) we switched to using inches. Computer screens have always been inches afaict.
Measuring boats in feet is a tradition. Also, these numbers are bigger. 50 feet is a big boat. Compare with mere 15 meters. BTW, docking price lists are still in meters.
If you carry a calculator in your pocket, but if you're just casually converting, 3 feet per meter is pretty good. 100 square meters is about 1000 square feet as well. Not legal for tax purposes, but good enough to understand how big a place is.
