Ok I was just rewatching this episode for like the 6th or 7th time and it clicks that there are 3 or 4 vans when Ben comes to the island.. We came across 1... So where are the rest of them?

If there were more than one van could there be more than one sub?

Just something that stuck out to me..

__________________
Please don't give up, Des. Because all we really need to survive is one person who truly loves us. And you have her. I will wait for
you. Always. I love you, Pen

DESMOND: I love you, Penny. I've always loved you. I'm so sorry. I love you!
PENNY: I love you too.
DESMOND: I don't know where I am, but--
PENNY: I'll find you, Des--
DESMOND: --I promise--
PENNY: --no matter what--
DESMOND: --I'll come back to you--
PENNY: --I won't give up--
BOTH: I promise. I love you.