Tricoastal, quadricoastal, and hexacoastal countries

Question

Let’s define a distinct coastline as a coastline you can theoretically walk completely without going through the territory of another country. For example, apart from islands, Mexico has two coastlines: one on the Pacific, and one on the Gulf of Mexico. On its main island, Ireland only has one, because even though it’s interrupted by Northern Ireland, you can still walk all the way from Drumskellan to Omeath without going through the U.K., by taking the long way around. Let’s count coastlines on oceans and major saltwater seas (e.g. the Mediterranean and the Black Sea), but not coastlines on inland seas (e.g. the Caspian and the Dead Sea).

By my count, there are 29 countries with multiple distinct coastlines on the same landmass, and most of them only have two.

1. Can you name the four countries in the world that have exactly three distinct coastlines on one landmass?

2. Can you name the three countries in the world that have exactly four distinct coastlines on one landmass?

3. Can you name the one country that has exactly six distinct coastlines on one landmass?

Answer 1

Answers

Can you name the four countries in the world that have exactly three distinct coastlines on one landmass?

Canada, Saudi Arabia, Malaysia, France

Can you name the three countries in the world that have exactly four distinct coastlines on one landmass?

The United States of America, Morocco, Russia

Can you name the one country that has exactly six distinct coastlines on one landmass?

Spain

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Explanations

One of the two countries with four distinct coastlines (by this definition) is

The United States of America.

The four coastlines (on one landmass) are:

Alaska, Point Roberts, the Pacific coast (Washington to California), the Atlantic coast (Maine to Texas).
If you count Great Salt Lake as fitting your definition of "major saltwater sea", you could even make a case for this being a 5-coastline country.

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This makes the second 4-coastline country:

Morocco

The four coasts are:

1. West of Ceuta
2. Between Ceuta and Peñón de Vélez de la Gomera
3. Between Peñón de Vélez de la Gomera and Melilla
4. East of Melilla
(Melilla credit to kaine)
(Peñón de Vélez de la Gomera credit to eudes)

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The final 4-coastline country is:

Russia

The coastlines are:

1. Black Sea
2. Pacific Ocean
3. Baltic Sea (Kaliningrad)
4. Baltic Sea (St Petersburg)
I don't include the occupied territory of the Crimean peninsula. That's still part of Ukraine, even if Russia has tanks rolling all over it.

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The 6-coastline country:

Spain

The coastlines here are:

1. Atlantic Ocean (north shore)
2. Mediterranean Sea (East of Gibraltar)
3. Strait of Gibraltar (West of Gibraltar)
4. The coastline of Ceuta across the Strait on Morocco's coast
5. The coastline of Melilla (credit to kaine on this 5^th coast) to the East of Ceuta on Morocco's coast
6. The coastline of Peñón de Vélez de la Gomera (credit to eudes on this 6^th coast) on Morocco's coast
.... Those sneaky Spanish!!

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The four three-coastline countries are:

1. Canada — Pacific Ocean, Boundary Bay, Atlantic/Arctic Ocean
2. Saudi Arabia — Red Sea, Persian Gulf (x2) (credit to Bailey M)
3. Malaysia — South China Sea (x3, split twice by Brunei) .. bonus+2 Malacca Strait split by Singapore (credit to kaine)
4. France — North shore, south shore (x2, split by Monte Carlo)

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Previously, I had listed Germany as a three-coastline country, but I suspect that Szczecin Lagoon is counted as a continuous extension of the Baltic Sea.

Answer 2

Some countries not yet mentioned (I assume that exclaves can be included, if on the same landmass):
2 coastlines:

1. Oman, because of Musandam Peninsula
2. Brunei – indeed, two parts!
3. Lithuania, on Baltic Sea "proper" and on Curonian Spit
4. Ukraine, if Crimea is considered in Russia (see below). Also, the region of Budjak is separated from the "mainland" Ukraine by the Dniester estuary, though of course connected through some bridges (see here) – but this probably shouldn't count as separate coastline.

3 coastlines:

Spain, because of Gibraltar, but:

6 coastlines

Spain, if we can treat Eurasia+Africa as one landmass, because it includes a few territories in North Africa, bordering Morocco, of which Ceuta, Melilla and Peñón de Vélez de la Gomera are parts of land.

And finally, with possibly 8:

Russia.
Depending on how we define a distinct coastline precisely, Russia may have even 8 of them (6, if excluding unlawfully annexed Crimea). I describe them below, according to maps I found, and let the reader decide on their own, which are right.
1. with the Pacific and Arctic Oceans, from Vladivostok up to Murmansk
2. with the Baltic Sea (Gulf of Finland), around St. Petersburg
3. (in the Kaliningrad Oblast) with the Baltic Sea (Curonian Lagoon), inside the lagoon
4. (KO cont.) with the Baltic Sea (incl. Vistula Lagoon), from the Lithuanian border on the Curonian Spit to the Polish border inside the Vistula Lagoon
5. (KO cont.) with the Baltic Sea (incl. Vistula Lagoon), on the Vistula Spit. However, the Strait of Baltiysk, which currently separates the spit from the mainland, is artificial, albeit old (1497)
6. with the Syvash lagoons of the Sea o Azov, from the Isthmus of Perekop to the de facto border with Ukraine on the Arabat Spit, just south of Strilkove village
7. with the Black Sea and the Sea of Azov, the remainder of the coastline of the Crimean Peninsula
The Crimean Peninsula is de facto administered by Russia. Hovewer, this administration isn't "recognised by most of the international community" (by en.wiki/Crimea), so 6 and 7 are not officialy in Russia.
8. with the Sea of Azov and the Black Sea, from Taganrog to Sochi.

Also, a comment, if I may (can't comment normally yet). It seems to me that

Germany has only 2 coastlines, because Szczecin Lagoon is connected with the rest of Baltic Coast – you can walk along Uznam Island.

Answer 3

Still a partial answer:

2 Coast lines:

- Germany - Spain - North Korea - Mexico - Guatemala - Hondoras - Nicaragua - Costa Rica - Panama - Columbia - Argentina - Turkey - Egypt - Isreal - Senegal - Croatia - Thailand - China (depending on how you view Hong Kong) - United Arab Emirates

3 Coast lines:

- Russia - Saudi Arabia - Canada - Malaysia - France

4 Coast lines:

- United states