the boat. The standard versions require a fin to be removed to get the foot into the stirrup, and have a fixed length, which can be awkward to use as the stirrup may be uncomfortably high for a tall person if at the right height for a short person. Adjustable versions allow the diver to clip the loop around the foot with the fin in place, then the loop can be raised to the preferred height after fitting. Open sided rigid "hook" stirrups allow the foot to be positioned on a rigid stirrup without removing the fin. Stirrup steps have the same ergonomic disadvantages as rope ladders: they swing freely under load. Boat diving hazards Run down by boat (the dive boat or any other passing by) Cut by propeller (the dive boat or any other passing by) Left behind in the sea after the dive Seasickness Another diver landing on top during entry. This can happen when divers do a group backward roll over the side of a boat, and do not all go in together. Anyone rolling late may land on top of someone already in the water. It can also happen when entries are from the same point and a diver does not ensure that the water is clear to enter. Falling overboard in transit, particularly when crossing a surf line after a beach launch in a boat where the seating is along the sides. Surfacing far away from boat and cannot be found. Surfacing away from an anchored boat and unable to swim back to it against wind or current. Hypothermia and wind chill on open boats in cold or windy weather Sunburn and overheating on open boats in hot weather Special procedures Some boat diving activities require special procedures to reduce risk or enhance the diving experience. Logging in and out The risk of being left behind by the boat can be controlled by logging divers into and out of the water. If this is done by each diver only for themselves, there is little chance of confusion and error. In other protocols the skipper or divemaster is responsible for ensuring there is a name-list of all divers on board before leaving the shore, and that everyone on the list is back on the boat before leaving the dive site. Use of personal marker Surfacing at the shot-line, group surface marker, or personal marker buoy