Making the River Navigable
The Derwent was made navigable under authority of the Statute, 1 Anne V. 20 (1702), which conferred powers on certain persons, called the undertakers, to make the river navigable from Scarborough Mills to Hemingborough, the point of its confluence with the River Ouse. The navigation was never commenced at Scarborough Mills, and from a case which was submitted in 1807 to the then Solicitor-General upon the grievance of preferential tolls it would seem that for the space of some 20 years after the passing of the Act the powers conferred by it remained dormant. The original undertakers did not appear to have exercised their rights, but probably disposed of them for valuable consideration, as about 20 years later the rights appear to have been acquired by Lord Rockingham, to whom the greater part of Malton then belonged.
Between 1720 and and 1730 two persons, supposed to have been lessees of Lord Rockingham, made the river navigable from Hemingborough (the lower end) to the beginning of the town of New Malton, by building 5 locks (which still remain) and doing some other trifling work - this part of the river being naturally in such a state that it required few alterations to make it navigable, and including 16 miles of tidal water. The outlay was understood to have been about £4,000 out of a total estimated outlay of £60,000 required to complete the navigation to Scarborough. 
 Malton in Olden Times, first article, Malton Messenger
The Malton and Hull Navigation Company
In the Malton Messenger of 1 January of this year the "Articles of Agreement" of the Malton and Hull Navigation Company were printed, from which it transpires that in 1837 the following gentlemen formed a company with the purpose of developing navigation between Malton and Hull.
James Dunlop, draper, Edward Rose, wine merchant; Robert Pickering and Henry Pickering, drapers; Abraham Sewell, grocer; Joseph Priestman and Isaac Priestman, tanners; Joshua Priestman and John Hopkins, curriers; Robert Woodroffe and Showler Woodroffe, ironmongers; Richard Tomlinson and George Kingston, brewers; George Barnby, stationer; William horsily, druggist; Joseph Taylor, factor; Robert Clegg, draper and grocer; Thomas Etty, wine merchant; Joshua Metcalfe, grocer; Thomas Taylor, grocer; Robert Rutter, boot and shoemaker; John Rutter, grocer; James Metcalfe, merchant; Charlotte Smithson, stationer (all of which reside in New Malton in the county of York); David Priestman, of Old Malton, in the said county, miller; John Slater, of the parish of Old Malton, aforesaid, nursery and seedsman; Robert Searle, of Norton, in the said county, grocer and spirit merchant; Edward Setchfield of the same place, raft merchant; and Benjamin Collins, of Scarborough, in the said county, gentleman.
The original capital of the Company was fixed at £2,500, divided into shares of £10 each.
Mr. X senior, used to tell his son that the Rye was navigable, at any rate as far as Newsham Bridge, which may well be so, as when the old Malton dam was demolished the Rye fell eight feet.
more to be typed
 Malton in Olden Times, first article, Malton Messenger in which the Malton Messenger columnist "Spectator" had discussed memories of an old resident of the town - his father was a waterman.
… a Government inspector under the Canal Boats’ Act had paid a visit to Malton and on enquiry he found there were three boats on the river to which the Act applied, and which must be registered forthwith… … Of the three on the river, one is the navigation boat … … leaving only two keels plying to Malton with merchandise. This state was contrasted with that existing 25 to 30 years ago when there were 20 vessels plying to Malton.
York Herald, 29 November 1884