How to tell if someone's talking about "the lakes" or "the seas?"

Question

If I'm talking to someone about the lakes and the seas — both die Seen — is there any way to differentiate between when someone's referring to one or the other at all?

According to the tables I was provided on Duolingo's "Nature 1" lesson, if we're talking about singulars it's easier:

sing.|  der See (m., the lake) | die See (f., the sea)
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nom. |  der See                | die See
acc. |  den See                | die See
dat. |  dem See                | der See
gen. |  des See                | der See

There can be some confusion since the dative and genitive cases for die See are der See, but those would generally be picked up depending on the way the sentence is constructed.

However, when we get to the plurals, everything looks the same:

plur.|  die Seen (m., the lakes) | die Seen (f., the seas)
----------------------------------------------------------
nom. |  die Seen                 | die Seen
acc. |  die Seen                 | die Seen
dat. |  den Seen                 | den Seen
gen. |  der Seen                 | der Seen

So... how can I tell these apart at all?
How do I know if when someone says Die Seen sind tief, they're saying that the lakes or the seas are deep? Especially in cases like just the above sentence, where we can't draw from the context of the rest of the conversation.

Or am I worried about too much of an hypothetical, and is die See simply not used all that much, in favor of das Meer?

Answer 1

According to Duden (the standard dictionary of German language) "die See" has no plural in the meaning of "das Meer". This means that "die Seen" is always a plural of "der See" (in the cases where it is obviously spoken about water bodies).

Answer 2

"Die See" is actually an entity name - with no plural, similar to "die Erde" / "Earth" (notice the upper case). It denotes the entire nautical environment and can be translated with both "the sea" or "the seas", depening on context. If one specifically wants to talk about multiple distinct "seas", then it's "die Meere" (both "die See" and "das Meer"/"die Meere" are used regularly).

Unfortunately, nouns are always upper case in German, so entity names like this are much harder to tell apart from the literal expressions compared to the English ones. In this case, you can safely assume "Die Seen sind tief" to mean "The lakes are deep" even without context.

PS: sing. gen. of "der See" is des Sees" ;)

Answer 3

According to Wiktionary, "die See" meaning "das Meer" (sea) is a mass term and hence always singular. "die See" meaning "die Welle" (wave) can hardly be confused with the meaning "das Meer" by context.

Answer 4

You are right in your observation die See in the meaning of sea isn't used too often. Most times in fixed expressions:

Wir fahren an die See.

We go to the seashore.

BUT

Wir fahren an die Seen.

We go to the lakes.

AND

Er fuhr zur See.

He was a sailor.

Er war Kapitän zur See.

He was a captain on a sea ship. (As opposed to a captain on a river boat.)

Die See ist stürmisch.

The sea is stormy.

seewasserfest

seawater proof

In most of the cases, das Meer is used instead.

Wir fahren ans Meer.

We go to the seashore.

Er fuhr auf allen sieben Meeren.

He was sailor on all seven seas.

Das Meer ist salzig.

The sea is salty.