O Código das Fronteiras Schengen contém várias disposições relevantes. Primeiro, o artigo 4 prevê que
[…]
By way of derogation from paragraph 1, exceptions to the obligation to cross external borders only at border crossing points and during the fixed opening hours may be allowed:
(a) in connection with pleasure boating or coastal fishing;
[…]
O Anexo VI fornece alguns detalhes sobre como isso deve funcionar na prática.
Pleasure boating
3.2.5. By way of derogation from Articles 4 and 7, persons on board a pleasure boat coming from or departing to a port situated in a Member State shall not be subject to border checks and may enter a port which is not a border crossing point.
However, according to the assessment of the risks of illegal immigration, and in particular where the coastline of a third country is located in the immediate vicinity of the territory of the Member State concerned, checks on those persons and/or a physical search of the pleasure boat shall be carried out.
3.2.6. By way of derogation from Article 4, a pleasure boat coming from a third country may, exceptionally, enter a port which is not a border crossing point. In that case, the persons on board shall notify the port authorities in order to be authorised to enter that port. The port authorities shall contact the authorities in the nearest port designated as a border crossing point in order to report the vessel's arrival. The declaration regarding passengers shall be made by lodging the list of persons on board with the port authorities. That list shall be made available to the border guards, at the latest upon arrival.
Likewise, if for reasons of force majeure the pleasure boat coming from a third country has to dock in a port other than a border crossing point, the port authorities shall contact the authorities in the nearest port designated as a border crossing point in order to report the vessel's presence.
3.2.7. During those checks, a document containing all the technical characteristics of the vessel and the names of the persons on board shall be handed in. A copy of that document shall be given to the authorities in the ports of entry and departure. As long as the vessel remains in the territorial waters of one of the Member States, a copy of that document shall be included amongst the ship's papers.
Eu não tenho experiência em primeira mão com isso e eu não sou um profissional legal então você deve levar tudo isso com um grão de sal, mas a minha leitura dessas regras é que, a menos que você tenha chamado em um porto fora do Schengen área ("vindo de um terceiro país"), você não precisa fazer nada. Mas as autoridades suecas ainda podem invocar o segundo parágrafo para realizar uma verificação de fronteira de qualquer maneira, então esteja pronto para fornecer todas as informações necessárias, se necessário.
noonsite.com também fornece muitas informações e, em particular:
Yachts arriving from a Schengen country (i.e. all countries bordering the Baltic Sea with the exception of Russia) do not have to notify Customs on arrival in Sweden if there is nothing to declare […]
The Swedish Coastguard recommends that vessels, even though it is no longer strictly required, continue to submit details of crew and passengers in advance.
O mesmo site também fornece detalhes de contato para os escritórios da guarda costeira, se você preferir contatá-los diretamente para obter a confirmação oficial de que você está autorizado a entrar na Suécia sem formalidades.