I live in Boulder, CO. We don't have beach sand here. I went down to a local place and bought truckload of WASHED river sand. River sand is generally washed commercially first before you buy it because it is used for lots of different things, including making concrete. Sand from places like Florida though is different from river sand. it is formed from coral and is loaded with cretaceous stuff and may not be as inert. I don't know how sand from tropical areas would work as a growing medium.
Sand from California though I believe to be essentially river sand because it is washed down from inland rivers and is made of inert mineral material. If you do use beach sand though I would suggest washing it first. It is highly porous so maybe just flushing it with fresh water will be sufficient to purge out all the salt.
I use an intermittent sprinkler to deliver the water as the plants need it. That way I don't have to use very much water.
Another note: Fine grained sand holds water more easily than coarse grained sand. The coarser the grains the more porous the sand is. Also, coarse grained sand provides more aeration for the roots.
I have been using medium to coarse grained sand which I think provides the best balance.