He was one of the seven young men left to overwinter in Quinnipiack in 1637, and he signed the New Haven fundamental agreement. He was a merchant, treasurer of the Colony, representative in 1652, magistrate in 1658. He moved to Milford in 1655 and went to Boston in 1659.
"Mr Jofhua Atwatter and Mary Blackman were Married by mr Ludlow at Stratford ye 6th of may 1651."  Mary Blackman was d/o Rev. Adam Blackman, They had 10 Children. After Joshua's death, Mary married Rev. John Higginson. She survived Higginson also and died 9 March 1709. She divided her estate (by her will) equally between daughter Ann Dummer, wife of Jeremiah; Mary (see below); and Grandaughter Rebecca, dtr of Joshua Jr. No sons were mentioned in her will.
He died 16 May 1676, in Boston, Massachusetts. His will mentions each of the children of his brother David. 
Samuell Atwater the fonn of mr Jofhua Atwater was borne the 20th of June 1654
Joshua Atwater, eldest son of Joshua, who grew to adulthood, was born in Milford 10 April 1658; bpt. in New Haven 21 Dec. 1658; married (1) Mehitable, d/o Francis Wainwright of Ipswich; married (2) Mary, d/o Seaborn Cotton, granddaughter of John Cotton and Governor Bradstreet. He had two or more children. He drowned 12th Feb. 1692
↑ 2.02.12.22.3 Jacobus, Donald Lines (compiler). Families of Ancient New Haven, Vol I-VIII. and Index Vol IX New Haven: 1931. Reprint, Baltimore: Genealogical Publishing Co., Inc., 1974, 1981, 1997. Originally published as New Haven Genealogical Magazine, Volumes I-VIII. Rome, NY and New Haven, CT 1922-1932.
↑ 5.005.015.025.035.045.055.065.075.085.095.10 Savage, James. A Genealogical Dictionary of the First Settlers of New England Showing Three Generations of Those Who Came Before May, 1692. Vol. I-IV. Boston, MA, USA: 1860-1862.