What to do in Swansea?

Hi, my girlfriend and I are coming down at the end of this month for my 19th birthday. I was just looking for advice from locals on where is good to go for nightlife, things to do in the day and what the easiest way to get about is. I think we’re staying near the beach next to the marina and i’ve noticed a few nice spots there, but i’d prefer advice off locals!

(some of you may ask why Swansea but we both love Wales and this a place in Wales we’ve never been before)