When I type in "Link: www.catamarans.com" or "Links: www.catamarans.com" into Google, I recieve different totals for sites linking to us. What is the reason for this?

Because you have a space between : and www. The proper command is link:www.domain.com.

The other two commands do not give proper totals when it comes to linking sites? The total I get from the command you gave me, gives way too low of a reading.