STOCKHOLM, June 16 (Xinhua) -- Water levels in Swedish seas and lakes are unusually low after a persistent heat wave, causing trouble for boat owners, with many running aground.

Boat repair shops are being kept busy in Sweden at the moment, Swedish Television reported Saturday, with many boat owners being forced to come in to fix propellers and gearboxes after hitting the sea bottom while leaving and arriving at docks.

"We are receiving customers who are used to driving where they always drive their boats. They know where there are stones and where the water is shallow, but then again I don't think the waters have been this shallow before," said Per Anarlou at the Nordwall Marina on the island of Lidingo in Stockholm, Sweden's capital city, which is surrounded by an archipelago.

The Stockholm archipelago is a cluster of some 30,000 islands, skerries and rocks and is just a few minutes away from the city, making Stockholm a particularly popular city for boat enthusiasts.

At another boat club on Lidingo, members said it has been hard even to get the boats out because the water is just too shallow.

Sweden saw a record-warm May this year, with more sun hours than ever before, according to the Swedish Meteorological and Hydrological Institute. The high pressure has been persistent in large parts of the country throughout June and has helped push water levels below average in both the sea and lakes. The lakes' water levels may also have been affected by the lack of rain over the past two months.

"What's required now in order to restore water levels in the Baltic Sea, for instance, is a low pressure and also south-westerly winds that would push water in from the Kattegatt Sea," said Swedish Television's meteorologist Per Stenborg.