The staff and Friends of Twin Lakes State Park will celebrate the end of summer with a beach party from 2-5 p.m. Saturday. There will be hula-hoop and limbo contests with prizes, and a natural tie-dying program by rangers. Beach-themed music will be played as visitors participate in activities or swim in Goodwin Lake. Swimming in the lake is $3 per child 3-12 years of age, $4 per person 13 years of age and older. Group swimming, per person for groups of 10 or more, is $2 per child 3-12 years of age, and $3 per person 13 years of age and older. Children under 3 swim for free. Natural Tie-die program is $4 per person. A $4 per vehicle parking fee applies.