The Access Code says:
Access rights can be exercised along riverbanks and loch shores except where a garden or other curtilage goes right up to the water's edge. Be aware that riverbanks and loch shores are often a refuge for wildlife and may be used for fishing and related management.
Show consideration to people fishing and keep a safe distance if an angler is casting a line. Some lochs and reservoirs are used intensively as commercial fisheries and so can be potentially dangerous where a lot of anglers are casting in a small area. Take care in such areas. If you wish to use a boat and there is a public slipway or launching point you should use it. Take extra care if you are passing by or landing on an island as these can often be a good refuge for wildlife.