Icebergs

[stakk]

Icebergs are materialized by small ice shapes with a penguin on it and with white oval around it. The action area of an iceberg is within the oval itself. Boats sailing in the oval area suffer a progressive reduction of their speed.
Icebergs move randomly at low speed. If an iceberg moves to a position at the north of buoys, it melts and disappears.
Icebergs can appear suddenly at any position but at a position south of the buoys.

The penguin is a protected species.