Why not get a seal to go for you instead.
Now admittedly, the sensor on this one is only collecting scientific data (location, temperature, water salinity, pressure etc.), but it wouldn’t be too difficult to include a camera, would it.
I went to a lecture last night about “seal scientists”, collecting data that research vessels can’t. The sensor pack is glued on, and has to weigh less than 1% of the seal’s weight.
They also put sensor collars on polar bears. When asked how, the lecturer responded “very carefully”.