Lundy Island is oriented north-south but it has an east-west tidal stream. This means that Lundy Island is prone to very strong tidal currents but provides effective shelter from them during the slack water period. Slack water for safe diving is about 2 hours either side of low water.
For more information and up to date tides and currents go to the following websites:
Lundy tides and currents
Lundy tide times