A relaxed touring paddle. You will want to time your run with the tide: the last 5km will be much easier if timed to be just after high tide, but be quick otherwise you'll have to struggle through the mud banks to get out.
Putin at the quayside in Carmarthen itself, or follow the B4300 out of Carmarthen along river left and access the river from a layby near Wenallt. Takeout at Llansteffan: either from one of the carparks or the boat house itself.
Rainchasers is best experienced as an app.