It is common to need to clean a slipway to remove fouling and algae. However, you should be aware that what you use to clean a slipway is regulated. 

A marine licence is not required from the Marine Management Organisation (MMO) for cleaning a slipway, although you may still require an Environmental Permit to discharge into surface or groundwater.

Any biocidal products containing active substances with the intention of destroying algae require Health and Safety Executive (HSE) approval. Any such product approved by HSE for use in and around water is accepted by the Environment Agency so long as the product is used in accordance with the conditions on the label. The MMO provide information on this. 

If you have any further information or feedback on using a slipway cleaner, please contact us at environment@rya.org.uk.