The spelling of /b/ is either <p> or <pp>. The spelling of /ʃ/ is usually <sh> but we also see <ch> in chalet and <ci> in social.
The contrast is between a voiced stop and a voiceless fricative, well separated in the mouth. There are no problems for any learners.
There are two taboo word pairs: bag/shag, and bat/shat..
Interesting pairs include
The mean density value is 2.3%. The list makes 135 semantic distinctions, a loading of 56%.
abbey ashy abbeys ashes B she baa shah baas shahs baa'd shard back shack backed shacked backing shacking backs shacks bacon shaken bad shad bag shag bagged shagged bagging shagging bags shags baggy shaggy baggier shaggier baggiest shaggiest bail shale bake shake bakes shakes baking shaking baker shaker bakers shakers bale shale ball shawl balls shawls ballet chalet ballets chalets bandy shandy bandies shandies bandoleer chandelier bandoleers chandeliers bank shank banks shanks bar shah bars shahs bard shard bards shards bare share bared shared bares shares baring sharing bark shark barks sharks baron Sharon barred shard barren Sharon bat shat batter shatter battered shattered battering shattering batters shatters bawd shored bayed shade bays chaise be she beak chic bear share bears shares bearing sharing beard sheared beat sheet beating sheeting beats sheets beau show beaux shows Beccles shekels bed shed bedding shedding beds sheds bee she beef sheaf beeves sheaves beep sheep beer shear beers shears beer sheer beet sheet beets sheets bell shell belled shelled belling shelling bells shells belle shell belles shells berry sherry berries sherries Bertie shirty beys chaise bide shied bier shear biers shears bier sheer biffed shift billing shilling bine shine bines shines bin shin bins shins boar shore boars shores board shored Bob Boche bode showed body shoddy bold shoaled bolder shoulder bole shoal boles shoals bone shown Bonn shone boo shoe boos shoes booing shoeing boo shoo booing shooing booed shooed boos shoos book shook boor sure boot chute boots chutes boot shoot booting shooting boots shoots bore shore boring shoring bores shores bored shored bought short boulder shoulder boulders shoulders Bourne Sean bout shout bouts shouts bower shower bowers showers bow show bowing showing bows shows bowl shoal bowling shoaling bowled shoaled bowls shoals bowman showman bowmen showmen box shocks bread shred brew shrew brews shrews brewed shrewd brill shrill brine shrine brines shrines brink shrink brinks shrinks buck shuck bucked shucked bucking shucking bucks Shucks bun shun buns shuns bunting shunting burke shirk burked shirked burkes shirks burking shirking burly Shirley bury sherry bush shush bushes shushes but shut butt shut butting shutting butts shuts butter shutter buttered shuttered buttering shuttering butters shutters buy shy buys shies buying shying buyer shire buyers shires buyer shier buys shies by shy bye shy byes shies byre shire byre shier cab cache cabbies caches cob cosh crab crash crabbing crashing crabbed crashed dab dash dabbing dashing dabbed dashed fable facial fables facials fib fish fibbing fishing fibbed fished fibber fisher fibbers fishers flabby flashy flabbier flashier flabbiest flashiest flabbily flashily gab gash gob gosh harbour harsher hub hush hubbies hushes job Josh knob nosh lab lash lubber lusher marble marshal marbled marshalled marbles marshals marble martial nab gnash nabbing gnashing nabbed gnashed rub rush rubbing rushing rubbed rushed slab slash slob slosh soberly socially squab squash stab stash stabbing stashing stabbed stashed
John Higgins, Shaftesbury, January 2010.