Shelter Bay Marina was created when the US turned the Panama Canal over to Panama in 1999.  It was formerly the docks of the US Fort Sherman.  Click here for the official Shelter Bay Marina website and contact information.

The marina is trying to be a first class, first world marina, but the reality of life across the harbor from Colon, Panama provides extra challenges.
The pricing is definitely 1st world and they charge for every little thing.  It didn't bother us because we knew it in advance, but some cruisers complained.  Be sure to keep tabs on your bill if you're there awhile so you don't get any surprises!  They had a problem with crime but added a fenced yard to keep boats on the hard and after that I didn't hear of any more missing stuff.

Fort Sherman is across the Panama Canal from Colon - providing a barrier for safety purposes since Colon is known as a "dangerous" city.   For the record, we followed local advice for safety, where to go and where not to go, when to take a cab, etc. and never had any problem, never even felt unsafe.
Your mileage could vary.  The marina provides a bus that goes to the Rey (supermarket) and other Colon locations multiple times a week.  Sometimes a bus trip to Panama City will be offered, sometimes not.  It is expensive to get anywhere via taxi since everyone has to stop and wait for the canal opening - it's rather common to be delayed a half hour and an hour wait wasn't out of the question.  Plan accordingly! 

One of the things we liked best about Shelter Bay was it's location nestled in the Chagres National Park and Fort Sherman.  Fort Sherman has been abandoned, leaving some interesting exploration.  The jungle is everywhere, making sightings of howler monkeys, spider monkeys, toucans and other wildlife frequent.  You can hike (or drive) to the fort at the entrance to the Rio Chagres, history abounds!