Castle Semple loch has high levels of blue-green algae. Water sports such as paddle boarding, kayaking, sailing, and windsurfing are okay as you should be able to avoid direct contact with the water. It is recommended that swimming or diving into the water from the pontoon is avoided. High levels can cause skin irritation or stomach upsets. Please wash your hands before eating food and shower/wash wetsuits if immersed. Dogs should be kept out of the water as they will lick their fur afterwards and this can lead to serious ill health that has in some cases been fatal. The image below shows the main two cyanobacteria in the loch – Gloeotrichia, that masses into a ball and Anabaena which links together to form a spiral shaped chain.