Most of the characters in Marine Benefit are original and non-existent in the Touhou Project. The following three are, however, officially part of the Touhou Project and are playable characters in Marine Benefit, each with three different shot types. The rest below are the originals.
Shrine Maiden of Paradise, Red Miko
The familiar shrine maiden. The hakurei shrine maiden. She does not seem to realize the perils of the sudden appearance of water. She was fed up with the summer, with all the sweat drying up. Having been called upon by Yukari Yakumo, Reimu went diving in the sea to cool down. Would she, who had always been floating, manage to arrive at the destination?
Ordinary Magician, Blue Magician
Gensokyo resident, ordinary magician, and carries a bad habit of collecting things. Suddenly, she had great interest in the sea. Since it was such a rare event, she sailed out in blue clothes. Although she looked for sailor suits, it seems like she wasn't able to find any. Her Mini-Hakkero probably stays active and does not rust even in the large amount of salt water.
Newbie Goddess of the Mountain, Green Miko
A Miko that lives in the Moriya Shrine on the Youkai Mountain. Not used to Youkai extermination. She was troubled by the continuing rain. She went to investigate the sea by the order of Kanako, even though she thought that investigating the sky would be a more appropriate method to stop the rain. Since Kanako said it, the cause is probably the sea. As memories of the sea floated into her eyes again, she proceeded to resolve the incident - something she isn't used to.
- Stage 1 Midboss/Boss
Konoha Susanomori (Failed Person with a History)
- Stage 2 Midboss/Boss
Naruko Uzushima (Innocent Youkai in a Whirlpool)
- Stage 3 Midboss
Miyo Amazu (Mass-changing Funayuurei)
- Stage 3 Boss
Tsubame Minazuki (Self-Confident Forecaster of the Sea)
- Stage 4 Midboss/Boss
Kasumi Shindou (An Oasis Under the Sea)
- Stage 5 Midboss/Boss
Megumi Yaobi (The Mistress of the Underseas Vigor)
- Final Stage Boss
Mikoto Yaobi (Mother Spring of the Sea)
- Extra Stage Boss
Otohime Kanpukugu (The Dropper of Dropped Items)