Vandals have wrecked a hut used as a Sea Scouts group headquarters in Lewes.
The yobs even brought rocks along with them to carry out the attack.
Scout leaders found stones unlike any others near the hut had been hurled through the windows.
The attack cost the 6th Lewes Sea Scouts more than £500 - half their annual income.
The attack upset local residents so much, one anonymous supporter has put up a £500 reward for information.
Meetings have been cancelled until further notice.
The vandals also broke a fuse box which sparked a small fire when the power in the hut was switched on.
Treasurer David Freeman said: "I don't know why anyone should target us."
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