[Note 419.1] The arrival of steamboats in 1819 and steam launches rendered the small Wherry, with its limited capacity, obsolete for mass public transport use, often the heavy wash from steamers rocked or sank thenk and frightened potential passengers away (See Bar279, The Nobby Waterman and Bar112, The Excursion to Putney). A fragment entitled "Gaieties of Greenwich" is held in the same British Library volume on the page facing this song. In part it reads:

"The fly or go-cart famed for the numerous robberies that took place in them during the war, still lingers 'down the line' doomed shortly to fade before the iron grasp of the railroad in its march to Dover.....On the river a similar change has taken place skiffs wherries and other small fry have so-to-speak been boiled by steam"

The watermen realised that opposition to the steamers was futile and in 1840 they formed the Waterman's Steam Packet Company with a fleet of 12 fast packets  (thus dating this song to 1840 or soon after). Their strongest rival at the time was the Woolwich Steam Packet Company (established 1834). The Steam Watermen deliberately timed their packets to start at the same time as the Woolwich Company's boats and racing was indulged in with no regard for the safety of their passengers or other river craft. [Dumpleton B, The Story of the Paddle Steamer] 

[Note 419.2] "The ladies all flock in these boats so readily...":- Steamers were bigger, more stable, and where they could be boarded directly from the riverbank, much safer than wherries. They were therefore, likely to attract wealthy women in expensive and unwieldy clothes.

[Note 419.3] The Adelphi buildings were the home of the well-to-do in contrast to the lower classes frequenting the Old Shades (see [Note 419.4])
[Ref: http://pubshistory.com/LondonPubs/StMartins/ShadesTavern.shtml]

[Note 419.4] Either Old Shades Wharf on the south side of Upper Thames Street, near Fishmongers Hall [British history On Line http://www.british-history.ac.uk/report.aspx?compid=63257#s8],
or a celebrated tavern, called The Shades which stood in Upper Thames Street and at Old Swan Stairs, built out from Old Fishmongers' Hall.
[Ref: http://www.british-history.ac.uk/report.aspx?compid=63306#s1]

[Note 419.5] "In parties to Greenwich" :- Greenwich was a popular place social gatherings.

[Note 419.6] Black funnels:- presumably the Woolwich company's boats

[Note 419.7] Nymphs, the Fairies, and Witches. Presumably the boats of rival companies.