The volunteer crew were on their way to a training exercise in Newhaven just after 7pm when they were alerted to three people in an inflatable boat near Saltdean.
One adult and two children were then rescued by the crew having been blown out to sea by an offshore wind.
Soon after the crew had returned their Atlantic 85 lifeboat Random Harvest to their station at Brighton Marina at around 9.23pm they were then called out to a report of a male in the water near the Palace Pier. The crew rescued the male and then passed him into the care of the emergency services.
Lifeboat operations manager Roger Cohen MBE said: ‘Our advice is not to use inflatables in the sea – please save them for the pool.
‘If you do decide to head down to the beach please stay near lifeguards, make sure children are supervised and stay close to the shore between the red and yellow flags.
‘It is vital to have a means of communication and safety equipment like a lifejacket or buoyancy aid.
‘Our crew are highly trained and ready to respond to emergencies but by spreading safety messaging we can hopefully make these call outs less frequent.
‘We know the beach is becoming busier now the weather is warming up so please share this information with your friends and family.’
The evening saw the first two shouts for trainee crew member Charlie Kelly who had joined for the routine exercise.
Charlie said: ‘I was excited to get my first two call outs in the same evening, it just shows it can happen at any time and the crew are always ready to react.
‘It was great teamwork making sure the four people who needed rescuing on Tuesday made it back safely onto land and I was able to use my training in a real-life situation.
‘We are expecting more call outs now the weather is warming up so it’s vital anyone going out on the water checks RNLI safety advice and has a means of communication with them.’