The King's Cross terminus of the Great Northern was opened in 1852. [i] The railways were the route into London for provincial folk in search of a better life or simply adventure.     Lewis Cubitt, King's Cross Station, 1851-52

References:
[i] http://www.networkrail.co.uk/aspx/867.aspx 
Picture: https://richardjohnbr.wordpress.com/2008/04/22/railways-operation-and-economic-impact/

Edward Yates wrote in his memoirs that "for one or two seasons there was a steamboat which left the adjacent Cadogan pier at the close of the entertainment, and carried passengers to Hungerford Bridge, and which was very popular." [i] Cadogan Pier is shown on the right in the picture below.
A search of the British Newspaper Archive reveals advertisements for steamers to Cremorne in 1861 , 1862 and 1863 [ii]. The West Middlesex Advertiser and Family Journal of Saturday 07 March 1863 reported that Cremorne railway station had opened. This is almost certainly a reference to the Chelsea & Fulham station of the West London Railway that opened on 2nd March 1863[iii]. No advertisements for steamers to Cremorne or Cadogan Pier have been found after that date, so seemingly the railway rapidly superseded the river boats.

ALLDIN'S COAL WHARF AND CADOGAN PIER, CHELSEA [Detail]  Signed and dated 1860 Walter Greaves (1846-1930)

References:
[i] Edmund Yates, His Recollections and Experiences, 1885 [chapter on 1847-1852] http://www.victorianlondon.org/entertainment/cremorne.htm
[ii] Hampshire Advertiser Saturday 22 June 1861; London Evening Standard, Monday 28 April 1862; West Middlesex Advertiser and Family Journal Saturday 07 March 1863
[iii] https://en.wikipedia.org/wiki/Chelsea_%26_Fulham_railway_station