Swimming Clamperl seems like a pretty straightforward request in New Pokemon Snap, but the solution isn't nearly as obvious as it may seem. Though Clamperl are commonly found all around the Blushing Beach and Maricopia Reef, the swimming Clamperl can only be found in the Lental Seafloor expedition once you've unlocked the stage's alternate route. Finishing the request will net you the four star photo of Clamperl for your Photodex, so if you're having trouble finding a Clamperl that can swim, here's a step-by-step guide to completing the Swimming Clamperl Request.
How To Complete The Swimming Clamperl Request
The swimming Clamperl can be found on the Undersea expedition in the Lental Seafloor zone. You won't be able to find the Clamperl until the Clawitzer busts through the rock at the beginning of the stage and opens up the course's alternate route. So if that hasn't happened yet, continue exploring the seafloor on multiple expeditions until you rank up and unlock this event.
The Clamperl is near the end of the course. To begin, pay attention to the left side of the track as you make your way through the opening shallow water biome. You'll eventually come across the Clawitzer swimming towards you from the alternate path. To take this route, you'll just need to scan to reveal the interact hovering in front of the path, then hold the scan button while aiming at the icon.
This will take you into the alternate route where you will descend deep into the ocean. This route will introduce quite a few Pokemon that do not appear on the main route, including Frillish, Lanturn, Golisopod, and Starmie. As you descend deeper into the ocean, you'll eventually encounter a Wailord swimming vertically towards the surface. This is your cue to turn your focus down towards the seafloor and look for your opportunity to find the Clamperl.
As you approach the seafloor, you should spot a Lumineon swimming near a blue shell that's partially buried in the sand. Your scan won't show it, but that blue shell is actually a Clamperl. All you need to do is toss a fluffruit near the blue shell and Lumineon will take care of the rest.
If your aim is good, the Lumineon will swim towards the blue shell and examine it. It will the dig up the Clamperl and fling it across the seafloor. This is your swimming Clamperl, and any photo you capture of it while it's "airborne" will count as a four-star photo and complete the request.
It can be pretty difficult to get a quality shot of swimming Clamperl considering that it isn't very close and it will fly quickly left to right across your screen. A good way to improve your rating with this photo is to use your boost to speed up ahead of the Clamperl, making it easier to catch a shot from a more frontal angle. Burst isn't particularly helpful here because you'll have plenty of time to line up your shot, so just focus on getting the best angle possible.