301 redirect problems with dynamic urls

Hi,

I'm trying to redirect the following url:

www.example.com/vessels.php?p=ship
to
www.example.com/ship.php

with the following code:

RewriteEngine On
RewriteCond %{QUERY_STRING} ^p=ship$
RewriteRule ^/vessels.php$ http://www.example.com/ship.php? [L,R=301]

but for some reason it's NOT working??

Can anyone help?

Thanks