March still gets Atlantic groundswell and has not yet met the summer wind. The nortada does not start until the end of April, so a March morning and a March afternoon are the same proposition, which is not true again until September.
That opens the whole country rather than one region. The central coast around Peniche and Ericeira is working, the Algarve has both of its coasts in play, and the north around Porto, Matosinhos and Espinho is at its best of the year. The water is still at 14°C, tied with February for the coldest, so the wetsuit does not change: a 4/3 and boots.

