Shared taxi from the airport to Serrekunda

Well to get a shared taxi (the yellow ones) you would first have to walk from the airport down to the main road which is a long way in that heat.
Strictly speaking the yellow shared taxi's are not really supposed to pick up from the arrivals at the airport but they can drop off.
There are plenty of green tourist taxi's outside the arrivals hall and the taxi controller will show you to the next in the queue and the fare could be between£10/15.
If you got a yellow taxi you would probably have to change taxi's a couple of times but if you share then it would be about 25/40 total but if you are the only one in and don't want to share then that's called a town trip and you will pay more so haggle a price maybe 200 dalasi.