With their efficient construction, we have more or less standardized on the new 2" housings for the in-cave flow sensors, and we are working with other research groups to redeploy the older 3" models as they get rotated out of the long term sites:

Field Report 2015-12-11: Flow Sensors go Farther & Deeper

Many of these new sites are in the open ocean, and are much higher risk for loss than we could have tolerated when we only had a few loggers to play with. But as a builder, I'm loving the challenges presented by the harsh environment. Forces me to up my game...