Wir fahren an den Strand. We go to the beach. Wir sind am Strand. We are on the beach.

Ich fahre an den Strand bedeutet das jemand in die Richtung fährt wo der strand ist. Wenn man dann einmal da ist fährt man auf dem strand. So: ich fahre an den Strand is a german colloquial expression.

To all Indo-European languages of all times (believe it or not), the following rule applies: When (local) prepositions can rule two different cases, then 1. the case for DIRECTION (where to?) is ALWAYS the ACCUSATIVE. 2. the case for place (where?) will vary according to the language, e.g. locative in Sanskrit, instrumental in Latin, prepositive in Russian, and dative in German. So, "an den Strand" (Akkusativ) can only be a reply to the question "wohin?"