We used all possible options of taking a bath (lake, bathtub, pool etc.)
Desmond: Would prefer a public pool, but not the public, public kind, but maybe the whirlpool. Some alone time, cheeky flirting – the other stuff will follow at home.
Altair: A small oasis, somewhere in the unknown desert. Would surprisingly be a little romantic with sweet love making under the stars.
Ezio: Bathtub. His famous bathtub scene was just too good for this world. Like Desmond, the other stuff will follow later on in his bed.
Connor: Down in the harbour of Davenport, the Aquila’s captain cabin will be the place for the fun~
Aveline: She literally calls for an adventure in the bathtub.
Edward: A little swimming competition in Nassau, before he lures you under deck.
Adéwalé: Would let you and your bath prepared and surprises you with rough, yet sweet love making.
Arno: The bathtub in his room is screaming for some wild action that splatters the floor with water!
Shay: Bathing in a small vowel, keeping you close – he’d be the snuggling type with passionate love making in his cabin!
Haytham: Would prepare a bath for you and him in the Green Dragon Tavern, forcing you to keep it quite, while he fingers you.
Shao Jun: Would give you a special treatment with her skills, she had as a concubine. Those, she would use, after the bath as well.
Arbaaz: The bath smells wonderful thanks to the spices he added, it would be a little bit inspired by the milk baths of Cleopatra and the room would be filled with your pleasures screams of lust and joy.
Evie: She would be a little bit flustered, doesn’t really know what to do, so you have to support and assure her a little bit. Sweet, innocent love making afterwards.
Jacob: Would visit a public bathhouse with you, hides there, after it closes its doors and would fuck you roughly while the moon glimmers on the waterskin.
-Sister Teodora.
Desmond: the kind of guy that would sneak in the shower, massage your shoulders and the get busy with you.
Altair: would probably bathe in the bureau in a large washbasin filled with oils and whatnot. You would join and he would complain at all, he would kiss you tenderly and make love to you.
Ezio: he would bath at the sanctuary or the public baths at late night. In both cases he would invite you to join him and he would take very good care of you by taking right there and then.
Connor: being the nature lover he is, the river and lake would be his preferred bathing sites, specially waterfalls. He might even surprise once in awhile by sneaking when you’re taking your bath, hugging from behind, whispering dirty things to you and taking you under the beating waterfall.
Aveline: since she was raised as a proper lady, she would run bath in her room and relax there, that is until you join her and aid her get clean, or dirty, you decide.
Edward: would probably find an island with a small river to take baths and taking you with him. The long make out sessions in the water, the way his hands would roam your wet skin, well let’s hope you can hold your breath for a while.
Adéwalé: much like a captain, he would retire to his cabin by the end of the day and prepare a bath to ease the tensions his body might have. You can join him, massage his taut muscles and drive him mad with pleasure.
Arno: would prefer to bathe in the Café Théâtre with you in the tub already waiting for him. He would strip for you and then get in to make sure you clean yourself everywhere.
Shay: would keep you very close to him in the washbasin in his cabin. He would relax with you, soothe your body with kisses and then get busy with you making quite a splash.
Haytham: Mr. Kenway has a love for spontaneous acts, so he would surprise you while you bathe and seduce you into perdition. He would help you bathe and kiss you and, ultimately, take you.
Shao Jun: since she was raised to be a concubine, her skills to make you feel good are well known to her. She would run a bath for both of you, massage oils on your skin, sing softly while doing so, then her touches would get more sensual until you can take it and you both fall prey to lust and desire.
Arbaaz: a connoisseur of spices, flowers and scents, he would prepare the ultimate bathing experience for you and enjoy the way to seem to relax in the water. He would slip in and touch you sensually, causing you to lose control over your actions and take him there.
Evie: would love to have her lover play with her hair and help her wash it, you would get in with her and help her until she decided she wanted help for something else, and well, you can deny Miss Frye, can you now?
Jacob: he and you would probably sneak in one of the rich people’s Turkish baths (which were quite popular back then, mind you) and there both would have fun with each other. The steam would heat up your bodies as he takes you passionately in one of the baths. Let’s hope you don’t get caught…
~Claudia
If you don’t mind, I’m going to change this up a little and use GIFs to respond to this ask (as I did before in the “What is the Assassins’ favourite place to kiss?” ask). Putting these under a cut. Again, I apologise to anyone using mobile! ;^_^
Desmond: All steamy goodness

Altair: Might ambush you while you’re taking a shower

Ezio: Would work those soap suds all over your body

Connor: Would carry you as you spend more time kissing than actually taking a bath

Aveline: Would demand that you clean her first (she will do the same to you, don’t worry)

Edward: Would attempt to make out underneath the water, of course

Adéwalé: Would ask that you go skinny dipping with him

Arno: All opulent and slow in a bath tub

Shay: Would hold you very close (a snuggler in the shower)

Haytham: Would surprise you and bathe with your clothes still on

Shao Jun: Straight to business ;D

Arbaaz: Would still be partially clothed while you’re completely naked because he’s a tease like that

Evie: All relaxed in a tub, would make out for hours if needed

Jacob: There’s no way he’s going slow when you’re both wet and slippery

~ Signora Paola