Properly watering entails maintaining an efficient irrigation system, one with a Smart-Timer, low flow components (like soaker tubing), adjusting sprinkler heads to minimize overspray, and
regularly checking the system for ruptures. Lawns are notoriously bad for the ocean - not only do they require a lot of water, but the run-off they produce is loaded with fertilizers and
herbicides. Instead of a lawn, consider the alternatives suggested by Surfrider.org.
Reducing lawn areas will reduce your long-term maintenance costs and signficantly reduce your water needs. Most lawn grasses are "cool season" grasses and require a great deal of water to maintain them. Large lawns are just not suited to most of the climates in which they are grown. Replacing unused lawn areas with desirable vegetation suited to teh growing conditions on your property can significantly reduce water needs.