The RNLI's D-class lifeboat at Penarth was called out to two incidents in quick succession on Friday evening.
The RNLI said its volunteers were called out at around 7.15pm to help two people who were cut off by the tide nearby.
Having contacted the coastguard by mobile phone, the pair were able to give a What3Words location which made it easier to locate them.
They were taken aboard the lifeboat and returned safely to the lifeboat slipway.
During the first shout, the coastugard received a call about a boat that needed help a couple of miles off Cardiff.
The 12ft vessel was found at anchor near the River Rhymney and taken safely by tow into the Cardiff Bay Barrage.
An RNLI Penarth spokesperson said in both cases, the casaulties involved had mobile phones to call 999 and ask for the coastguard.

Bro Radio partners with Hospital Radio Glamorgan for Cardiff Half Marathon coverage
Senedd Members reject Reform bid to scrap 20mph speed limits
Barry Town Council Cuts Public Opening Hours After Rise in Abuse Towards Staff
Opposition leaders clash with First Minister over Welsh independence
Santa’s Cause returns as Vale communities urged to support families this Christmas
Elderly Penarth couple call for generator to be relocated or replaced on health grounds
Police Appeal After Two Injured in Late-Night Fight Outside Barry Nightclub
Graduate turns personal experience into campaign to combat student loneliness
Further education one of Wales’ “greatest success stories” says former education minister
Vale of Glamorgan Football League Round Up 26/9
Body discovered in woods in Penarth
Three national award nominations for Bro Radio
Plans to restore historic Barry pond and boost local wildlife
Barry exhibition captures the changing face of Wales’ historic chapels
Senedd commission faces first questions in the Siambr following summer recess
Welsh Greens Leader Anthony Slaughter Reveals Cancer Surgery During Senedd Recess
Principality Stadium lands fight of the decade Joshua v Fury
Free Bleed Control Kits Offered to Community Groups Across the Vale of Glamorgan