Karis Hedges was returning from Skomer Island, Pembrokeshire, when she saw the seal "chilling out".
The 26-year-old started snapping away and captured some "lucky shots" of the mammal in the inflatable boat.
Ms Hedges, from Llandeilo in Carmarthenshire, said she was really surprised to see the seal.
The large animal, blatantly unbothered by its audience appeared completely relaxed.
Photos taken by Ms Hedges, who is a full-time photographer, show the brazen seal peering up towards its onlookers on 19 May.
Ms Hedges added that the boat was coming into shore and was moving quite quickly, so she only had a few seconds to capture the image.
"I thought it was really cute that he was totally unfazed by anyone and just chilling out without a care in the world.
"His expression is like 'and? Do you have a problem?' Like it was the most normal thing," she said.
Ms Hedges said she believed the seal had climbed into a boat's rescue dingy, adding the crew would probably have to kick out the surprise guest at the end of the day.
Ruyi Bridge is a footbridge in Taizhou, Zhejiang China, made up of three bridges. It is a pedestrian bridge which was built to cross the Shenxianju Valley and it features a glass-bottomed walkway. The unusual curved walkways are designed to look like a Chinese ruyi.
Total length: 330 feet
Height: 460 feet
(my bad on the small images shown, if you click them, they are larger)
What are all those streaks across the background? Satellite trails. First, the foreground features picturesque rock mounds known as Pinnacles. Found in the Nambung National Park in Western Australia, these human-sized spires are made by unknown processes from ancient sea shells (limestone). Perhaps more eye-catching, though, is the sky behind. Created by low-Earth orbit satellites reflecting sunlight, all of these streaks were captured in less than two hours and digitally combined onto the single featured image, with the foreground taken consecutively by the same camera and from the same location. Most of the streaks were made by the developing Starlink constellation of communication satellites, but some are not. In general, the streaks are indicative of an increasing number of satellites nearly continuously visible above the Earth after dusk and before dawn. Understanding and removing the effects of satellite trails on images from Earth's ground-based cameras and telescopes is now important not only for elegant astrophotography, but for humanity's scientific understanding of the distant universe.