Slowbro (all forms and family) gets waterfall via hm

polishedcrystal/data/pokemon/base_stats/slowbro_plain.asm

Line 24 in 3c76999

    
           	tmhm DYNAMICPUNCH, CURSE, CALM_MIND, TOXIC, HAIL, HIDDEN_POWER, SUNNY_DAY, ICE_BEAM, BLIZZARD, HYPER_BEAM, LIGHT_SCREEN, PROTECT, RAIN_DANCE, SAFEGUARD, BULLDOZE, IRON_TAIL, EARTHQUAKE, RETURN, DIG, PSYCHIC, SHADOW_BALL, ROCK_SMASH, DOUBLE_TEAM, FLAMETHROWER, FIRE_BLAST, SWIFT, AERIAL_ACE, SUBSTITUTE, FACADE, REST, ATTRACT, FOCUS_BLAST, SCALD, DRAIN_PUNCH, WATER_PULSE, AVALANCHE, GIGA_IMPACT, FLASH, THUNDER_WAVE, SURF, STRENGTH, WHIRLPOOL, AQUA_TAIL, BODY_SLAM, COUNTER, DOUBLE_EDGE, DREAM_EATER, ENDURE, HEADBUTT, ICE_PUNCH, ICY_WIND, PAY_DAY, SEISMIC_TOSS, SKILL_SWAP, SLEEP_TALK, SWAGGER, TRICK, ZAP_CANNON, ZEN_HEADBUTT

As mentioned in title, per serebii slowbro (kanto and galar) and slowpoke and slowking get waterfall via tm 77

https://www.serebii.net/pokedex-sv/slowbro/