I have used a suction style oil changer that I also use to drain my raw water pick up filters. Yes they have drain plugs on them but I hate draining several litres of water into the bilge. Comes out to 2 full containers worth of water that equates to close to 12 litres just for the 4 stainers.
After playing around with a DIY dry bilge pump setup this summer I elected to get one just for this purpose as opposed to using the oil changer.
A pump like this.
https://www.amazon.ca/SAILFLO-Pressure-Diaphragm-Caravan-Marine/dp/B071HV4DZ3?pd_rd_w=nClh4&content-id=amzn1.sym.ccd66d6a-fd89-4716-b3af-012410ff4aa9&pf_rd_p=ccd66d6a-fd89-4716-b3af-012410ff4aa9&pf_rd_r=3REWPMP52KYF3MAAKA29&pd_rd_wg=lzNhQ&pd_rd_r=baa3abd3-c002-409b-9c97-ba3e64b480e9&pd_rd_i=B071HV4DZ3&psc=1&ref_=pd_bap_d_rp_2_t10' of really soft 3/8" ID x 1/2" OD silicone tube.
https://www.amazon.ca/gp/product/B08FJ9869N/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1To power it I guess one does have 12v batteries on board however they are usually difficult to get to and would requires some long wires. I happen to have some 4S lipo batteries I use for RC stuff so plugging in one of those works very well and will last hours.
Pump directly into a shower sump and let it dump overboard or a small bucket and dump overboard manually.
There is always something that requires pumping out water in tight places such as an overflowed shower sump or just standing water the bilge pumps cannot get out or the PWC bilge. It now resides in the boat as a tool to use as required, actually pumps really well and self primes no problem. I was surprised to see gunk/crap being sucked up and run through the pump without issue, easily seen through the transparent hose. The silicone hose is very flexible and is easily pushed directly onto the pump inlet/outlet and easily removed. Tight enough to not require clamps however one can alway install some if so desired. For about a $50 investment it is well worth it to have this practical tool on board IMHO.
Back to the Lipo RC battery. Have used these for boosting cars on many occasions, believe me, they do pack some serious power.
I was in a parking lot and this guy had a dead large conventional booster pack which was obviously not working for him, I walked up and told him I would get mine. He actually laughed at me when he saw what I was going to use but then wanted to know where he could get one after his car started up instantly.
They do sell them ready made however after opening up a very powerful one and seeing the tiny battery in them, I decided to make my own long ago. I keep one of these on board as a boosting device such as the PWC or a boater in distress and powering anything 12v when in a bind. This little device will easily boost a large V8. Only issue is you need to be careful as there is no short circuit/polarity protection on one like this. Tie the 2 together and you will get quite the light show.

Here is a picture of the one I keep at home. The one on the boat is even smaller.
IMG_0396.jpg