Some of the ROV components need to be encased in epoxy to protect them from the water (e.g. the lights, the electronics for the manipulator, and the ESCs). I tried out three different epoxies:

• MG Chemicals 832C
• West Systems 105/205
• QSil 216

My ideal is something that's transparent, thermally conductive, electorally insulating, easy to mix and pour without bubbles forming, and - in case of problems - reversible. To try these out, I mixed up each epoxy and cast a small amount in acrylic boxes. I also mixed each epoxy again, but this time I vacuumed the epoxy before pouring in an attempt to reduce bubbles.

The photo below show the results:

On the left are the vacuumed samples, the non-vacuumed on the right. From top to bottom the epoxy are MG, West, and QSil. For my purposes, the QSil is the best: it's completely transparent and pours, even without vacuuming, without bubbles forming. As an added bonus (hopefully!) it forms a hard gel but does not go completely solid; in theory and with work it should be possible to remove. The only, minor, downside is that it takes over 24 hours to fully cure. Don't be in the rush.