I am also descended from Thomas Seamans and Susannah Salisbury, and have a bit of information on their lines going both forward and back.
Thomas's (who was b. abt. 1658 in Suffolk, England) father was Thomas Seamans (b. 1632, Norfolk, England), who married Elizabeth Copeland (b. 1638, Suffolk, England).His father was possibly a William Seamans (b. 1597, Suffolk, England) who married Elizabeth Dunkan or Duncombe.
Susannah's (b. 1662, Boston, MA) father was William Salisbury (b. 1622 Denbighshire, Wales), who married Susannah (White?) (b. 1624, Boston, MA).There is further history on this line in a book called "The Seamans Family in America" by J. Lawton, Syracuse, NY 1933.
According to that book an ancestor Adam De Salzbury went to Wales as commander of an army of William the Conquerer's, and 14 generations back from him the Salisburys are descended from Henry Guelph, Duke of Bavaria, his father Rudolph II, Duke of Bavaria, and mother Itha von Oeningen.
My line from Thomas is through his son Thomas (b. 1693), who married Martha Wood (b. 1697).Their son was Aaron Seamans (1733, Swansea, MA), who married Lillis Martin ((1732).Their son was the Reverend Aaron Seamans (b. 1768 Rohoboth, MA) who married Elizabeth Roe (b. 1771 Williamstown, MA).Their son was Alvah Seamans (b. 1812 Northampton, NY) who married Hannah Campbell (b. 1837, OH).Their daughter, Mary Paulina Seamans (b. 1861-62) was my great grandmother.