For those of you who like to trail to new grounds Cardiff Bay is worth a visit. There is an excellent slipway at Channel View Leisure Centre at Jim Driscoll Way, which is owned by the City council , where launching and parking cost £11 (including a £5 deposit) . The Bay itself is quite sheltered with no speed limit when clear of the rivers (Taff and Ely) Both Rivers can be explored for a short distance The Taff into the City Centre past the Millenium Stadium, The Ely past the white Water centre
and Cardiff Marine Village onto some narrow but quite secluded spots. The main attraction is Mermaid Quays where you can tie up to the pontoons with a pay and display machine which is again very reasonable. There are also overnight berths available. Mermaid Quays is very busy in the summer months with numerous bars and restaurants (the Cosmo oriental buffet is a favourite with a lunchtime eat as much as you can for £6.99) You will be spoilt for choice with Italian, Turkish, Indian, Chinese, American, Traditional and good old Harry Ramsden all within 100m of the berths. There is plenty of accomodation available including the bay front St Davids and the popular chain hotels. The beautiful Millenium (again) Centre and a bowling alley, nightclub and multiplex are again within a few hundred metres and if you are a Dr Who or Torchwood fan then you are exactly where a lot of it is/was filmed.
The Bristol channel is freely accessed at all states of tide through the Barrage locks with Penarth and Barry Island (Gavin and Stacey) a short distance to the West. Weston Super Mare is a short hop accross the channel with Flat Holm and Steep Holm Islands of interest. The Victorian seaside town of Penarth is just outside the Barrage locks and due to it's Eastward facing beach it is sheltered from the prevailing South Westerlies , it is home to Penarth waterski club and has been the venue for many international waterski events. The club is still very active and have the sole permission to ski in Cardiff bay on designated days.
I would highly recomend you put Cardiff on your must visit list