Familarise yourself with the shore line so you can use this for reference when sighting as any marker buoys at sea tend to be further apart than those in lakes and not always clearly visible. The shoreline can therefore prove an invaluable reference when disorientated.
Give yourself plenty of time to arrive and register as this is one less thing to think about.
Listen carefully to the race briefing and safety advice, it will give you essential information about currents – strength and direction; you can then work out from the race route whether/when you will be working against or with currents/tides.
If you are swimming in the sea for fun always check with the lifeguard before going in to find out what sea conditions are – tide times and currents. Pay heed to the flags marked out on beaches and at sea as they are there for your safety!
If wearing a wet suit, scoop water into it once you’re wearing it to provide a thermal level and help you acclimatise quicker
Drink plenty of fluids before and after your swim, especially if conditions are hot as you’ll dehydrate surprisingly quickly when wearing a wet suit.