Believe it or not, some underwater drone companies aren't supplying hobbyists with a cable reel or spool for letting out more tether for your underwater drone. This is a big nuisance with the Gladius Mini, so Mini owners have take it upon themselves to buy their own cable winder for this particular ROV. Luckily my Geneinno Titan T1 comes with a spool, so I don't have to go through the hassle of finding way and also figuring out a way to attach the wireless relay to the spool, as the Geneinno had a genius idea of making the wireless relay magnetic, so it snaps on the spool very effortlessly.
Here's a small video of a Gladius Mini custom spool on Facebook, the cable winder seems to be letting out line very smoothly without having to even pull on the tether to let out for more slack. I'm starting to see some Mini owners just use industrial velcro straps to attach the wireless relay to the spool, pretty neat idea.
Video on Facebook
And if you haven't noticed in the video up above, Youtuber Peter Lehnér 3D prints out a plastic round insert that fits right into the hole of the spool, then he slides in the velcro straps in the slits of the plastic insert, then he easily straps the wireless transmitter to the spool. Very ingenious idea!