You can get 1L Scuba for 211.59 USD using coupon code (in Banggood). You can create price alert here, copy coupons and view price history. Let’s see what best price is ATM.
Latest coupon and price update (UTC):
Banggood (211.59 USD)
Banggood warehouse is located in China. Low/high price? Hmmm, price is higher than average (which is 178.62 USD right now), so better set price alert down below… You can use 2 active coupon codes for this product!
Link: Banggood product page
Price without coupon: 229.99 USD
Coupon (211.59 USD): BGSPRING8OFF
Coupon (211.59 USD): BGHONEYSP
(CouponsFromChina.com tip: apply it in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BGBFDAY8
(I don’t think these’re gonna work, but you can try ’em out anyway)
Aliexpress
Click here… to search for DIDEEP X4000Pro 1L Scuba Diving Tank Snorkel Equipment on Aliexpress
Here are coupons that you can use.
Price history and price alert
Here is price history (for all/most countries) for DIDEEP X4000Pro 1L Scuba Diving Tank Snorkel Equipment.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).