There are plenty of things to see and do. The package holiday operators will offer a number of excursions, but all of these are available through local tour offices too, so don't worry about missing out if you are travelling independantly. Try the Lazy Day Cruise on the creek when you are ready for a rest!
There are also trips you can organise yourself. Try Ghana town, Tanji and Sanyang by taxi - fish are caught and smoked in these little villages for sale in the markets and there is a wonderful beach at Sanyang. You could visit Banjul, the capital, for a look around. You could also hire a vehicle and go a little farther afield - to Janjanburreh (Georgetown) on McCarthy Island or the slavery museum at Jufureh.
If you do drive yourself, bear in mind that the roads up
river can be very poor (although they have been greatly improved on the North side of the river recently) and the ferry between Banjul and Barra can be a
bind. Travelling East from Barra, you will pass through Kerewan (where the road gets bad) to Farafene (where it improves again). You can continue East from here to get to the ferry to Janjanburreh, or visit the stone circle at Wassou and perhaps get a boat from Kuntar the rest of the way (about an hour) and you may see hippos.
There are plenty of fishing and bird watching oportunities. Sea fishing boats or beach casting equipment can be hired locally at the beach and creek fishing can be organised through a tour office or Janes Boats.
The monkey park at Bijilo is easy to get to and nice if you like monkeys.