Wondering who Freeland is.
Could he have been a Presbyterian? There was Presbyterian minister of that name in Kingstown, who seems to have been well known at this time.
The following entry in CH Irwin's "A History of Presbyterianism in Dublin and the South and West of Ireland" is interesting and suggestive...
Rev William Freeland.
About 1822 services were commenced in
a loft in Dunleary, and were conducted by members
of the Dublin Presbytery. The services were after-
wards held in a loft in the harbour workyard, duly
seated, and were well attended. 1 In 1827 the congre-
gation was formally organised by the Presbytery of
Dublin, and the first minister, Rev. William Freeland, LL.D., was ordained there on Sabbath, June 1st, 1828 [……………]Dr. Freeland was a man of
much ability, and a very instructive expositor of Scripture. He was for a time very popular. His ministry was attended by many members of the then Established Church, including Fellows of Trinity College, naval officers and others. But some disagreements having arisen between him and members of the congregation, his usefulness in Kingstown became impaired, and by the advice of the Synod of Ulster he resigned in 1838. He afterwards became minister of Ballygawley congregation, which, however, he resigned in 1841.

This Captain H Robinson seems to be Captain (later Admiral) Hercules Robinson. (1789-1864) He was a son of the Revd Christopher Robinson, Rector of Granard, Co Longford, and a grandson of Sir Hercules Langrishe of Knocktopher Abbey, Co Kilkenny. There is an entry for him in the Dictionary of National Biography. He was a veteran of Trafalgar and commanded a ship called the Promethus for 5 years which was a sluggish vessel, and only by great guile and stealth did he capture any enemy vessels. He commanded a ship called Favourite in the area of Newfoundland and Labrador and some of his interesting accounts from this work were published in the journal of the Royal Geographical Society in 1834.
His Christian work included involvement with the Naval and Military Bible Society, and being Honorary Secretary of the Hibernian Sunday School Society (Sunday School Society of Ireland).
While on the Prometheus he conducted a Treasure Hunt on the Salvage Islands (now recognised as Portugese islands between Tenerife and Madeira, to find treasure allegedly buried there from a Spanish Galleon. He reprised this treasure hunt in 1856, and wrote a book called “Seadrift” –which covers the treasure hunt, but also contains a rambling autobiographical account of interesting events, mingled with his opinions on a huge variety of matters. It is an engaging and amusing account and exhibits much breadth of knowledge in many fields and one concludes that he was an interesting character, while being in many ways a modest man with a spirit of Christian contentment. A recent (2010) book has a whole chapter on his treasure hunt exploits which includes photographs of his original correspondence to the Admiralty. (The Selvagens, Forgotten Atlantic Islands by Alex Ritsemal. 2010. Published by Lulu. ISBN10 1446189686)

Thanks! A link to the Sea-Drift book on Google; https://books.google.co.uk/books?id=pjUBAAAAQAAJ&pg=PP11#v=onepage&q&f=false