Freeport has its own town park on the ocean:
 Winslow Park

In addition, the southern coast of Maine offers many state parks to visit:

Wolfe's Neck Woods State Park - (http://www.state.me.us/cgi-bin/doc/parks/find_one_name.pl?park_id=31)

Reid State Park - (http://www.state.me.us/cgi-bin/doc/parks/find_one_name.pl?park_id=13)

Popham Beach State Park - (http://www.state.me.us/cgi-bin/doc/parks/find_one_name.pl?park_id=22)

Bradbury Mountain State Park - (http://www.state.me.us/cgi-bin/doc/parks/find_one_name.pl?park_id=12)

For more State Parks in Maine: (http://www.state.me.us/doc/parks/programs/db_search/index.html)