Abstract: A retractable thruster for a swimming vessel is provided, wherein the retractable thruster includes a propeller and a lifting and lowering arrangement which is configured to vertically move the propeller between a retracted position and an ejected position. In the retracted position the propeller is substantially inside a bottom well of the swimming vessel and in the ejected position the propeller is substantially outside the bottom well. The retractable thruster includes a water-permeable protective element configured to be located inside the bottom well above the propeller and configured to vertically move with the propeller. In the ejected position the water-permeable protective element is configured to substantially prevent loose ice from drifting inside the bottom well through the water-permeable protective element and when the propeller is moved from the retracted position to the ejected position, the water-permeable protective element is configured to push ice out of the bottom well.