Re: Mass at the beach?
Seems clear to me:
Redemptionis Sacramentum regarding where Mass may be celebrated:
1. The Place for the Celebration of Holy Mass
[108.] "The celebration of the Eucharist is to be carried out in a sacred place, unless in a particular case necessity requires otherwise. In this case the celebration must be in a decent place".197 The diocesan Bishop shall be the judge for his diocese concerning this necessity, on a case-by-case basis.
"May Mary, who bearing Jesus in her womb was the first living "tabernacle" of the Eucharist, communicate to us her same faith in the holy mystery of the Body and Blood of her divine Son, so that it may truly be the centre of our life."
--Pope Benedict XVI