▁and ▁mang ro ve ▁for ests . ▁The ▁shape ▁of ▁a ▁beach ▁depends ▁on ▁whether ▁the ▁waves ▁are ▁construct ive ▁or ▁destruct ive , ▁and ▁whether ▁the ▁material ▁is ▁sand ▁or ▁sh ing le . ▁W aves ▁are ▁construct ive ▁if ▁the ▁period ▁between ▁their ▁wave ▁cr ests ▁is ▁long ▁enough ▁for ▁the ▁breaking ▁water ▁to ▁re ced e ▁and ▁the ▁sed iment ▁to ▁sett le ▁before ▁the ▁succeed ing ▁wave ▁arriv es ▁and ▁breaks . ▁ ▁Fine ▁sed iment ▁transport ed ▁from ▁lower ▁down ▁the ▁beach ▁profile ▁will ▁compact ▁if ▁the ▁re ced ing ▁water ▁per col ates ▁or ▁so aks ▁into ▁the ▁beach . ▁Comp act ed ▁sed iment ▁is ▁more ▁resist ant ▁to ▁movement ▁by ▁tur bul ent ▁water ▁from ▁succeed ing ▁waves . ▁Con vers ely , ▁waves ▁are ▁destruct ive ▁if ▁the ▁period ▁between ▁the ▁wave ▁cr ests ▁is ▁short . ▁Sed iment ▁that ▁remains ▁in ▁susp ension ▁when ▁the ▁following ▁wave ▁cr est ▁arriv es ▁will ▁not ▁be ▁able ▁to ▁sett le ▁and ▁compact ▁and ▁will ▁be ▁more ▁sus cept ible ▁to ▁er os ion ▁by ▁long sh ore ▁curr ents ▁and ▁re ced ing ▁t ides . ▁The ▁nature ▁of ▁sed iments ▁found ▁on ▁a ▁beach ▁tends ▁to ▁indicate ▁the ▁energy ▁of ▁the ▁waves ▁and ▁wind ▁in ▁the ▁local ity . ▁ ▁Con struct ive ▁waves ▁move ▁material ▁up ▁the ▁beach ▁while ▁destruct ive ▁waves ▁move ▁the ▁material ▁down ▁the ▁beach . ▁During ▁seasons ▁when ▁destruct ive ▁waves ▁are ▁pre val ent , ▁the ▁shall ows