Moominpappa at Sea (Swedish: Pappan och havet, literally "The father and the sea") is the seventh book in the Moomin books by Finnish author Tove Jansson. It is based primarily around the character of Moominpappa. It was first published in 1965. Moominpappa at Sea forms the basis of episodes 25 and 26 in the 1990 TV series. The original title is a loose reference to Hemingway novel The Old Man and the Sea, though this is not reflected in the translation. This is the second book in the series whose name is a Hemingway-reference.
Moominpappa is dissatisfied with his life in Moomin Valley, so he organises the family to set off on a journey to find a lighthouse in the sea. This will also be the perfect backdrop for a novel about the sea. Once arriving there, they find it a desolate and lonely place, inhabited only by a very unfriendly fisherman. Moomintroll also befriends The Groke and the sea horses. Moominmamma misses home so much that she starts painting the Moomin house with lots of flowers since none can be grown on the lighthouse island. Later they find out that the fisherman is actually the lighthouse keeper who fled from the loneliness.
Nature and the sea play a big part of the novel as Moominpappa tries to understand it, and there are many strange things happening on the island that seem to be inexplicable.
The map at the front of Moominpappa at Sea locates the island in The Gulf of Finland. It even gives a location: Latitude 60° 7' 12" North, Longitude 25° 45' 50" East. (Not far from Helsinki, about 26 miles east of Helsinki, and 7 miles south of the coast of Finland; though no island exists there in real life.)