Or you could Google "Swansea Marina" and you'll get a pdf document of their marina booklet which has the local tide times in.

I'd agree with everything Graham and Mr Bloto has said. I always refer to the chart, no matter how many times I've done it because there are a few sand banks there and you just need to be vigilant. You can usually see them before you get too near, because the water whitens and foams on them. Keep a close watch on your position and echo sounder, and you'll be in Wind Street on the lash in no time.

Enjoy your trip,

Lizzy D