Visa questions for cruise ship arrival in St. Petersburg

Question

We will be arriving in St. Petersburg on a cruise on July 18 and leaving on July 19.  We don't want to do the organized tours through the cruise company.  We want to get a tourist visa and see the city independently.  We will sleep on the ship.  

I assume we need a multiple entry visa and we will have to go through immigration each time we leave and return to the ship.  Is this correct?

On the request form for visa support (for multiple entry), it is asking for travel dates (1st entry, 1st exit, 2nd entry, and 2nd exit).  I'm a little unclear on how exactly I should do this.  Should I complete it like this:

Entry 1: July 18
Exit 1: July 18
Entry 2: July 19
Exit 2: July 19

I am confused if this is the way to do it or a single entry would suffice simply with an Entry date of July 18 and exit date of July 19.