The Island's coastguard is warning people with jetskis and fast craft boats to keep out of areas designated for swimming.
There are Safe Bathing Areas around the Island which the service says should only be used for emergencies or for launching.
The coastguard has produced a booklet and a map to show where these areas are.
Parts of the shore off Douglas, Castletown, Derbyhaven, Port St Mary, Port Erin, Peel, Ramsey and Laxey are all included in safe bathing list.
The coastguard says people should be able to swim in the sea safely without fear of coming into contact with fast moving craft.
It goes on to say any boat or jetski owner asked to move by the coastguard or harbour officer must do so immediately.
The map highlighting the no-go zones can be found at any coastguard or harbour office or can be downloaded online from the Isle of Man Harbours website.