Category: Sailing

The Environment Agency/Briggs Marine are scheduled to undertake a small scale scientific survey (sediment grab sampling) in the Caernarfon Bay area from the vessel Severn Guardian.

Survey Details

Survey Period: 07/04/2026 – 23/04/2026
Survey duration: 2 days
Time on station: 15-60 mins
Survey Vessel: Severn Guardian
Skipper: Mark Williams
Survey Officer: Tom Lord [email protected]

Station	OSGB36 Easting	Northing	OSGB36 OS Reference	DD.DDDD DD	Long DD.DDDDD	DD°MM.MM MM’	DD°MM.MM MM’
CAERN_1	239280	361992	SH 39280 61992	53.130783	-4.403765	53°07.8470’N	4°24.2261’W
CAERN_2	240832	361471	SH 40832 61471	53.126572	-4.380327	53°07.5943’N	4°22.8196’W
CAERN_4	238263	360637	SH 38263 60637	53.118366	-4.406132	53°07.1019’N	4°24.3679’W
CAERN_5	240341	357819	SH 40341 57819	53.09366	-4.385842	53°05.6172’N	4°23.1506’W
CAERN_6	238946	357409	SH 38946 57409	53.09043	-4.406453	53°05.4258’N	4°24.3872’W
CAERN_8	241276	353524	SH 41276 53524	53.055325	-4.369768	53°03.3195’N	4°22.1861’W
CAERN_9	235278	358288	SH 35278 58288	53.084604	-4.451153	53°05.0762’N	4°27.0692’W
CAERN_12	243950	347509	SH 43950 47550	52.961015	-4.421605	52°57.9408’N	4°25.6606’W
CAERN_13	231147	348006	SH 31147 48006	53.002663	-4.517861	53°00.1598’N	4°31.0741’W
CAERN_18	243907	360290	SH 43907 60290	53.111536	-4.401007	53°06.6922’N	4°24.0604’W
CAERN_19	241302	359327	SH 41302 59327	53.107452	-4.372259	53°06.4471’N	4°22.3369’W
CAERN_20	237878	361000	SH 37878 61000	53.118084	-4.453248	53°07.0850’N	4°27.1949’W
CAERN_21	239993	355372	SH 39993 55372	53.037578	-4.480073	53°02.1467’N	4°28.0047’W
CAERN_22	238150	351600	SH 38150 51600	53.053778	-4.480079	53°03.1467’N	4°28.0047’W
CAERN_23	242151	342151	SH 42251 42151	52.949333	-4.423998	52°56.9600’N	4°23.9985’W
CAERN_24	228285	341382	SH 22825 41382	52.942268	-4.559601	52°56.5361’N	4°33.4176’W

Aid to navigation Port No C2 Fl.R 10s is on its appropriate station.

53° 07’.17 N 004°24’.32 W

David John O’Neill
Harbwr Feistr Caernarfon Harbour Master

Mariners are advised that between 8 March 2026 and 14 March 2026 there will be heightened commercial vessel traffic operating in the area identified on the above chart, particularly during periods around low water slack.

This traffic will include barges and seagoing tugs which may need to hold sta on for extended periods. All vessels and barges will be displaying the appropriate day shapes or lights.

Mariners should navigate with caution and maintain a safe distance from the vessels. If in any doubt, mariners should make contact with the standby vessel Delta2 on VHF Channel 16.

Overnight, large vessels will be anchored in the vicinity of the marked ‘X’, displaying the required anchor lights.

For press enquiries: Press Office – UK Highways: Call 0844 693 1448 – this is a 24/7 number. Journalists are requested not to contact individual departments. The Press Office will assist and arrange an appropriate spokesperson if required and may be contacted on 01248 752130 or 01248 752128.

This notices self-cancels at 11:59pm on 14 March 2026.

Harbwr Feistr Porthaethwy/ Menai Bridge Harbormaster
Ebost/Email: [email protected]

Aid to navigation C2 is not on its appropriate station.
53° 07’.13′ N 004° 24’.35 W

Mariners are advised to exercise caution in this area.

David John O’Neill
Harbwr Feistr Caernarfon Harbour Master

Mariners are advised that the Swelly Rock South Cardinal is now lit.

53° 13’.16N – 04° 10’.45W

Notice to Mariners 33/2025 is hereby cancelled.

David John O’Neill
Harbwr Feistr Caernarfon Harbour Master