No direct sun exposure.
Fresh tattoos should be kept out of direct sunlight at all times during the healing phase.
After around 1 week:
Once the top layer of skin has peeled off, you can use SPF 50 sunscreen for short periods outside. This is a practical temporary solution, but it does not replace fully covering the tattoo during longer time in the sun.
No chlorinated water.
Please avoid chlorinated water such as pools.
Freshwater and saltwater are generally fine, but only with strict sun protection. That means keeping the freshly tattooed area covered when swimming as well as outside the water.
Do not scratch or pick at peeling skin.
Let the skin shed naturally.
No sauna.
No tanning beds.
Avoid both for the full 3 weeks.
Showering is completely fine.
Water can go on the tattoo normally. Shower gel may run over it, and shampoo can also run over it without any issue.
Water temperature and shower length are generally not a problem.
Fresh tattoos can be a little more sensitive to heat than usual, but you will notice that immediately and can adjust if needed.
Personally, I usually recommend cleaning the tattoo mostly with water only. If something gets on it that should be washed off properly, simply use a little soap briefly and rinse well