Gracias Johan
Al final ha quedado resuelto de esta manera.
Playa is south of Bosque. The description is "Estás en una larga playa desde la que se divisa una lejana isla. Puedes ver muchas palmeras por aquí.". Understand "playa", "litoral" and "ribera" as the Playa
Some palmeras are here. They are female and scenery. The description is "Altas palmeras se extienden a lo largo de toda la playa.".
Instead of taking the palmeras, say "No puedes cortar las palmeras. Si quieres madera vete al bosque.".
Costa is here. It is female and scenery. The description is "Estas aguas son tan bellas como peligrosas, piensas mientras observas la diminuta isla, allá a lo lejos.". Understand "mar", "oceano", "línea", "aguas", and "agua" as the Costa.
Isleta is here. It is female and scenery. The description is "A lo lejos puedes visualizar una pequeña isla, tu destino.". Understand "atolón", "insula", "islote", "arrecife", "cayo" and "isla" as the Isleta
[ NADAR ]
swimming is an action applying to one thing. Understand "nada a/en/hacia-- [something]", "nada hacia la [something]", "bucea a/hacia-- [something]" and "bucea hacia la [something]" as swimming.
Instead swimming the Costa:
say "Decidido, te internas dentro de las aguas del mar y comienzas a nadar con fervor hacia tu destino. La isla...[paragraph break]";
wait for any key;
say "Tras un gran esfuerzo arrivas a tu destino. Pisas la arena de la playa, a cuatro patas, jadeando por la falta de aliento... [paragraph break]";
wait for any key;
now the player is in Isla.
Instead of swimming the Isleta, try swimming the Costa.
Carry out swimming:
say "Por aquí no veo agua en la que bucear.".